They could theoretically do it with the PS3/PS4 by allowing you to copy the save file off to a USB and then import it. It would probably be quite difficult doing it that way though because then Madden PS4 would have to be able to decipher NCAA PS3 save files. The other way would be if they allowed you to somehow upload to a website or something, it parses the PS3 file and then the PS4 could download it.

My bet is that they end up skipping draft class import on next gen for this year.