I would not be surprised to see goblin added as a playable race. There are a TON of gobo fans in the D&D community. In the end it'll be up to how vocal they are. Also, and I respect Larian for not soliciting things like this, but if a few wales threw some money at them to add goblins, I bet they would.
It's one thing to convince the studio that it may be worth to add the race because of its popularity, buy I don't think it's the sort of feature that can be "paid for" by a single generous donation. THe full implementation of a race, with models, textures, variations, in-game content to acknowledge its existence, etc... would probably cost in the order of the tens of thousands. And I'm being conservative here.