I don't think a cut off date was mentioned. So long as you put the disc in/play it before the Vita version comes out, whenever that comes out..., you should get Deadlocked for free... whenever that comes out to.
Interesting to note that Tin Giant have updated their website a bit:
Tin Giant
http://www.tingiant.com/staff.html
At least one former Insomniac and one past Idol Mind person that did the R&C HD collection.
And they list these as their projects:
http://www.tingiant.com/projects.html
Ratchet & Clank Future: A Crack in Time
Resistance 2
Ratchet & Clank Future: Quest for Booty
Resistance 3
Ratchet and Clank: HD Collection
Ratchet and Clank: Full Frontal Assault
Fuse
Now, they are either just listing all Insomniac's PS3 games (Bar Fall of Man) or they really are working on porting Insomniac engine/all Insomniac's games, to Vita. Including the PS2 one's i bet.