A crossover title would've been a good call. I can't tell if they're unaware how many skipped the PS3 or if they actually those that did are gonna buy a basically dead system for this series.
Hopefully they'll do to the remixes what they did to FFX. Port it so that console spread will actually be dealt with for once. Don't even need some fancy new collection, just ports.
It is a bit weird that they didn't do it from the beginning, as for example titles like Dynasty Warriors 8: Xtreme Legends got a simultaneous PS3/PS4-release from the get go. There exists even a transfer-option for save- and character-data from PS3-version to PS4-version and vice versa.
I also find it hard to believe that Sony would lobby for a PS3-exclusive release, as while the PS4 was only in its starting levels when HD 1.5 was released, a simultaneous PS3/PS4 release would certainly have not hurt.