It'll be operational to coincide with GT7's release in 2018.
I'm sure it'll work. I had OnLive and that worked just fine, the graphics were clearly worse and there was some lag but it was playable from the few hours I put in to it. I'd expect Gaikai on PS4 to be an improvement. Knowing Sony it'll take them two or three years to make it functional.
The Gakai thing won't work. I'll be really surprised and very impressed if Sony can pull it off.
Hated, adored, never ignored.