Lana did seem very certain that Regina had a big kill coming up, and at the time they’d only seen the first couple of scripts. I reckon they’ll wanna show us more of Tamara’s story still, but we’ve already got most of Greg’s, so he’s more expendable in the immediate future.
You know, I completely forgot about that spoiler from CC. Off topic, but I think Lana saying her favorite kill was coming up lends even more credence that 302 is in someway connected to Tamara.
If Regina does kill Tamara, which I think is very likely, what happens to Greg? She may not want to raise a hand against him given that she’s trying to redeem herself and she has already killed his father. But he’s not wholly innocent either. She may be perfectly happy to let Rumple take care of Greg. Or even PP. Send Greg back to PP with the knowledge that she has killed Tamara. PP riiiiiiiips off Greg’s shadow and more or less becomes his slave.