With the new arrival of the Wii U, it could be possible. They might try to go side by side with it like they will be doing with the Playstation Vita (going against 3DS at the same price). But Majesticuba does have a point with the 10 year cycle, they might stick to tradition and get all the life they can from the PS3 as they can. All in all, it's still a great console, and I do kinda hope they are making a PS4.
Also, I know this isn't Sony, but when Nintendo Released 3DS we started finding out about the Wii U. Well Sony is releasing the Playstation Vita so maybe we'll find out about a PS4? And if they do break the 10 year cycle, then who knows? Maybe they'll even break the naming cycle.