EDIT: It appears Microsoft has mislead us again, in exactly the same way they did with GTA4.
The official press release states:
"LEIPZIG, Germany — Aug. 23, 2006 — Once again proving that its game platforms offer more ways for gamers to have fun, Microsoft Corp. today announced great new games and accessories for Xbox 360™ and Windows® gamers. Delivering on the worldwide demand for Xbox 360, Xbox Live® and Games for Windows, Microsoft revealed key additions to its Windows Vista™ showcase library and Xbox 360 titles today at the 2007 Games Convention in Leipzig. In addition to announcing new European-centric board games for the hugely successful Xbox Live Arcade on Xbox Live, the premier online gaming service, Microsoft announced that the next generation of soccer will be available exclusively on the Xbox 360 console this year. With “FIFA 07” from Electronic Arts Inc. (EA) and “Pro Evolution Soccer 6” from Konami Digital Entertainment Inc., Xbox 360 will be the only place where gamers can enjoy next generation soccer this year."
What this means is that FIFA 07 is only exclusive because it was never officially announced for PS3 and that there will be no PES6 on the PS3 in 2006. There is no deal between Microsoft, EA and Konami, Microsoft just pointed out the facts in a way that makes it seem they have an exclusivity deal.
Therefore, FIFA 07 could still be released on the PS3 in 2006 and PES6 is only exclusive to 360 until the start of 2007 (although I doubt that's due to a deal, it was probably just never planned to be on the PS3 at launch, which suggests that the PS3 will have a re-worked version), meaning that on January 1st 2007, the PS3 could have both FIFA 07 and PES6.