It won't cost Sony anything extra to include 4K support, modern graphics cards are already capable of that resolution and HMDI spec 1.4b (which includes 2160p60) should be finalized at the end of the year.
(The ps3 can already output 4K images btw)
Maybe GT6 will be able to run in 2560x2160 on ps4. GT4 to GT5 went from 640x540 to 1280x1080, no reason why the same resolution jump can't be done again. 4k tvs will be affordable by the time GT6 comes out...
The ps4 is going to be around until 2021 at least. It's not unreasonable to buy a new tv in a 9 year period. How many people had a 1080p tv in 2004? (2 years before the ps3 launch)