Taking the rumors from canonrumors.com and some forum posts seriously for at least a bit, it seems that an announcement for a possible Canon EOS 5D MKIII is imminent.

Random Info via canonrumors:

• Canon Australia has sent CPS management to Singapore for product training. [CR2]
• Any Canon announcement will come after Nikon’s announcement on August 24, 2011. [CR2]
• 5D Mark III’s are in the wild and an announcement is imminent [CR1]
• 1D Mark IV’s are out of stock or hard to come by in certain countries. A retailer in New Zealand actually said they won’t be getting any more. [CR1]
• 1Ds Mark IV resolution correction, I’m told it will actually be 36mp.

Since I was planning on getting a 5D Mark II these days, I hope to see increasing price drops on the camera kits very soon - since there are already visible price drops around the globe. On Amazon.com the price for the Body still is $2499,00. Canon Australia already lowered the price for the premium KIT from $4899 AU$ to 4499AU$, so we can hope for price drops on the international market as well. On the German Amazon Marketplace, the currently cheapest price for the 5D MKII Body (new) is 1924,90 EUR, while the Premium KIT (EF 24-105mm L IS USM) is at 2619,99 (a light price drop is already visible).

Commenting on the current question, if it is still a good idea to buy a Canon 5D MKII: YES. Why? The Canon 5D MKII is a great camera and also there won't be any new Lenses coming up so fast (at least when we talk about EF 24-105mm L IS USM), so if you need one now, go and get one. Also, if you are in DSLR-Video, "Magic Lantern" is a great and stable system, which will not immediately run on the MKIII. Some people even suggests that there might be a 1000$ price difference (at least) for an upcoming 5D MKIII.

Conclusion:
Still the 5D Mark II is a good buy, when compared to the Canon EOS 7D, since an announcement for a Canon EOS 7D MKII won't be around the corner until end of 2011, if we believe the rumors. A 5d MKIII won't be available instantly after release, so one way or the other, before 2012 you won't be able to get your hands on a 5D MKIII - and if so, then for sure not for a reasonable price. The current price difference for the 5DMKII to the 7D is 700$ - if you are into DSLR Video, that's a clear GO for the 5DMKII.

[Update] Canon Rumors has a new Blog post "5D Mark III & The Rest [CR2]" which indicates, that there could be a 5D Mark III announced in October 2011

CODED CULTURES. Creative Practice out of Diversity

MO 4. April  2011, 19.00 Uhr

KUNSTHALLE WIEN - project space karlsplatz http://esel.io/termin/50759

Zur Präsentation sprechen: Christian Reder (Universität für angewandte Kunst Wien), Georg Russegger (Coded Cultures), Matthias Tarasiewicz und Michal Wlodkowski (5uper.net)

Eine Veranstaltung im Rahmen der Kooperation zwischen der Universität für angewandte Kunst Wien und der Kunsthalle Wien angewandte@project space mittwochs (www.dieangewandte.at)

http://j.mp/codedbook
http://codedcultures.org

A fresh book, discussing creative practices of the fields of media arts ("art with media" and "art through media") in europe and asia (mostly japan). To quote the official press statement: "International Authors from Europe and Asia explain the impact of codes and cultures on society". The book is available on Amazon EUROPE and the US Amazon site.

The short information is as follows:

"Through the transformations of creative cultures, enabled by digital media and global communication networks, new practices and ability profiles of artistic delineations and explorations are gaining grounds. New global codes and cultures are emerging out of diverse, intercultural abstractions and inventions, connected through new ways of exchanging ideas and sharing knowledge. At the present day it is difficult to predict which catalysts and draft programs can be put into effect for the development of near future playgrounds in this domain. By offering several perspective shifts on developments in digital realm and mediated reality, exemplary theories and projects on the intersection of different codes and cultures have been collected for this book. Presenting essays, reviews and interviews from international artists, theorists, researchers and curators, gives the reader an overview on new vectors of creative and artistic projects departed from digital media related art and cultures. It introduces new and critical models of observations on the intersection of disciplines like art, science, technology and design."

Coded Cultures. New Creative Practices out of Diversity (Georg Russegger)
Projects ... Project Worlds ... Project Cultures (Christian Reder)
Co-Evolutionary Anthropology of the Medial / CAM (Manfred Faßler)
Art is about the Future; Otherwise, Nothing (Hiroshi Yoshioka)
A Political Intervention in the Digital Realm (Marina Grzinić)
Assembling Art, Design, Technology and Media Culture: The Challenge of Japanese Device Art (Machiko Kusahara)
The Future of Creative Commodities in the Coded Cultures (Dominick Chen)
Coded Cultures Between New Media Art and Production Cultures (Matthias Tarasiewicz)
The Balance of my Wildness and my Intelligence was Way Off (David d’Heilly/Ujino Muneteru)
Mouseology—Ludic Interfaces—Zero Interfaces (Mathias Fuchs/exonemo)
Imaginary Agents—Flowers and the Common (Verina Gfader/BCL)
Ludic Chindogus as Erotic Toys— Pleasure, Play, and Politics Beyond Materialism (Margarete Jahrmann)
Urban Playgrounds, Alternate Games—on Urban Play, ARGs, and Psychogeography (Verena Kuni)
From Somebody’s Desire to Everyone’s Responsibility (Yukiko Shikata/UBERMORGEN.COM)

CODED CULTURES and MINIMAL TOKYO are proud to present a special night of electronic dance music at UNIT/SALOON. The night will feature top international and Japanese artists working in a wide range of music styles from deep electronica to minimal house and techno.

FENNESZ, from Austria, is undoubtedly the world's most influential electronic musician of today. The Rolling Stone magazine described him as "the most pictorial composer-programmer in laptop electronica". His ongoing collaboration with Ryuichi Sakamoto has received the highest international acclaim. TOM ELLIS, from Wales/UK, composes unique and highly distinctive blend of minimal house and techno with the essence of funk, jazz and rock. His releases on Telegraph, Minibar and more then 20 other labels received glowing reviews from music press around the world. EVALA and ATAK label founder KEICHIRO SHIBUYA are Tokyo artists, who produce some of the most progressive electronic sound in Japan.

このたび、CODED CULTURESとMINIMALTOKYOはエレクトロニカ、ミニマルハ
ウスシーンで世界的に活躍するアーティストを招待し、UNIT/SALOONにて音楽イベ
ントを開催いたします。
オーストリア出身のFENNESZは現在エレクトロニカ界で最も影響力のあるアーティ
ストの一人です。ローリングストーン誌はFenneszを「視覚的想像力に訴えるエレクト
ロニカを創る作曲家、プログラマー」と評しています。また、過去に坂本龍一とのコラボ
レーションで話題を集めました。イギリスウェールズ出身のTOM ELLISはファンク、ジ
ャズ、ロック、ハウス、テクノのエッセンスを取り入れた新しいダンスミュージックを作曲
しています。TrimsoundのレーベルオーナーでもあるTomは最近ではMinibarや
Telegraphからも精力的にリリースしており、日本でも人気を集めています。EVALAと
KEICHIRO SHIBUYA(ATAK)は日本で活躍するエレクトロニカアーティストで、その
新しく斬新な音が注目を集めています。

See the Flyer or the Event on the minimaltokyo page. Highly recommended!