I have both PS3 and Xbox 360 and apart from Uncharted 2 there isn't a really great game thats not available on the XBOX. If I had to choose 1 I would choose the XBOX. Why?..... Halo, Gears of War, Mass Effect, Left 4 Dead. Having said that the PS3 is worth buying just for the 2 Uncharted games. Also if you dont want to watrch live TV you can not pay a TV license and just watch BBC iplayer on the PS3!!. (All legal - I have had my setup checked by the TV licensing inspectors!!)
Its a great idea to have both, i do. I mainly do all my gaming on my xbox 360 and play online on xbox live. As for PS3. I mainly use it to play the exclusives and use it as a multi media center as it has massive HHD space and blu ray. But yeah, Xbox 360 is great and no, there woun't be a new xbox console for some time although it is possible they might make a slim xbox 360 but that will not change its features, just the size.