After Paramount made that announcement, Michael Bay quickly responded in his own forums with...
Subject: Wait a Minute!
I said I was taking off a year from Transformers. Paramount made a mistake in dating Transformers 3 - they asked me on the phone - I said yes to July 4 - but for 2012 - whoops! Not 2011!!! That would mean I would have to start prep in September. No way. My brain needs a break from fighting robots.
Michael
Besides meaning that the film will likely be needing a push back, it also confirms that Michael Bay is heavily invested in the franchise and is looking to wrap up the trilogy behind the camera. At this point in time, he is not contractually obligated to do so.