Yeah, I'd pick one up eventually, especially if the starting price is $400 or less.
Probably I'd wait to finish out my backlog on PS3 and then move after a price drop/revision, for sure. I mean how else am I going to play fighting games with the GGT?
As for Gears? Unless MS changes their policy or you concede to be abused by their DRM, you won't be playing any more Gears games already. Yes, you'll miss out on Uncharted, or whatever Sony exclusives you might want to play, but you missed out on most of those without knowing what you were missing until your 360 mishap and adoption of a PS3. I'm not saying never get a PS4, just maybe consider PC as another option.
Yes, you'd need to have a keyboard or mouse of some sort -- but if you did it right, you could just use your iPad to launch most games once your PC is built. I fully plan on controlling my gaming PC by the netbook that sits here with me most of the time and getting a wireless/keyboard mouse for games that are better off being controlled by those.