I don't really see him doing this with a boat as you'd probably stack off with a 7 anyway. Wouldn't he want to let you draw to the flush with a half pot-ish bet, which also can induce a raise from a weaker made hand? If he has quads then there are less hands the hero will stack off with but the likelyhood that he'll stack off if he has one of them is 100%, so there's no reason to play quads this strong either.

I'd say his range here is air/flush draw/7x/TPTK/overpair. I'd call with 87+, and AA/KK if I thought he's cabable of doing this with AQ looking for a hero call from Qx.

If we were at the river then I'd have to think long and hard about calling without a boat.