According to Gamespy, and the other links which follow, a Ubisoft employee may have inadvertently let the cat out of the bag regarding Sam Fisher's leap from exclusivity of the Xbox360 and PC and taking hostage of the PS3 in the future.

If this rumor works out to be accurate, Splinter Cell: Conviction would be released later in the year, as Xbox likely has the time exclusivity on sales such as they do with downloadable content (a regular Microsoft cash grab). The question is: will you wait to play as Sam Fisher on the PS3, or be like thousands of others who have already pre-ordered their copy for the Xbox/PC?

You will see in the links below that the Ubisoft employee removed the PS3 from his list of games he had worked on, but it may already be too late depending on which direction this rumor goes. Splinter Cell has always been a multi-platform franchise. It would be unwise and less profitable to prevent the highly anticipated fifth installment from being released on PS3.

Sources:
Playstation Lifestyle
Gamespy

On another note, I may have stepped into a clue for the 'sixth' Splinter Cell. While in Toronto, participating as a winning contestant to the "Inside Splinter Cell: Conviction Challenge" hosted by Ubisoft and Xbox, I discussed Conviction with a lead developer (who must remain anonymous). Unfortunately, I'm unable to disclose any information about that currently either. All I will say is that Sam Fisher's appearance is obvious.