My launch 60gig PS3 could play PS2 games. lol
But it's not really a big deal, it simply would have been nice and convenint for me personally if i could take all my bought digital content across to the PS4 and still play them.
How it would have worked with me is i buy a PS4 at launch, ditch the PS3, happily play all my PSN titles, very very occasionally get a PS4 game or sub to the PS4 version of PS+........while enjoying things like party chat on the new PS4.(I am assuming the PS4 is going to have some form of chat like XBlive).
But its not really a big deal, i can live with my PS3 for a good few more years.