Most likely not.
This is clearly based on the GT5 engine, with tweeks to the engine for PS3/PS4 and graphics for PS4. Clearly they want to get another one out to catch the tail end of PS3 and have a racing game out there as a PS4 launch title.
PS3 and PS4 have a substantially different architecture, with the PS4 obviously much much more powerful but substantially easier to program for, to really use the full potential of the new console, PD will mostly like need a new engine or substantially revise the GT5 maximize the benefits of PS4.
However, I will not be surprised is this had already been done for GT6/PS4 as PD and SONY had a special relationship when it comes to GT, very likely they are the first developer to get priority info/updates for anything related to PS4.