I dont recall Thresh ever saying he wouldn't and I dont see any reason why not, so I'd say the possibility is high, tho we must keep in mind that we are a long ways away from that type of content being implemented in the game, (likely multiple years away)so for now lets just stay optimistic! :]
Not inability, they directly state they eat the sperm/essence to prevent pregnancy it's the main trait of monster girls in this verse, consuming adventurers essence to grow stronger while also negating pregnancy.
If they ever develop more the romance side of it we may have it at some point either with the one chose as our "wife" or maybe accidental against certain opponants upon defeat.
