I think it will undoubtably boost sales for Vita but It may not come into real effect well into 2014 once the ps4 userbase is fairly big.
Many Wii U owners stated that off-screen play is one of the best things about the system, however the wii U can't sell itself on that alone, it needs the games. PS4 line up is already looking more healthy then the wii U and with gaikai the Vita's remote play could extent beyond the home. obviously the extent of the sales bump depends on the price of the Vita+sony's marketing. But again we won't see this straight away, I can't see too many people spending $600+ on A ps4+PSvita within the same holiday period.
And people please stop comparing it to ps3 remoteplay, there are like 3 games which work on it (ICO/SOTC, GOW collection Tokyo Jungle) and Sony hasn't advertised that feature of outside of a press conference demo.







