No, the whole series isn't being remade. I wouldn't be surprised to see RE2 getting the treatment at some point, but for now REWii will be an all-new title, based on the RE4 engine most likely but tweaked to take better advantage of the more powerful hardware.
Sought The Poltercow said:
Yeah, I wonder why SEGA are releasing it on DS too? Because they might have had an agreement with Sony, Sony might be mad
Probably didn't get the sales they expected after the DS ones were such a run away success. They've not done too badly, but nowhere near as well as the Nintendo ones, so they'll be looking to replicate that success on debatably the only system that can do them justice. I can't imagine a Brain Training-style game working on any other system than DS really.