I don't really get this attitude. There haven't really been any solid signs that Blizzard is closing shop on SC2, we just expect them to because we know that the game isn't successful right now. So we blame them for not investing more time in order to make it successful and then deduce from that lack of investment that they have given up on the game and in a remarkable twist it's suddenly their fault, ignoring all the while that it's by far the most successful game in a genre that is simply not popular anymore.

Starcraft is one of only 3 (4 with Overwatch) franchises that Blizzard has, it's not going anywhere. The idea that they'd abandon that universe is ridiculous not just from a gamer's perspective but from an economic one as well. There probably won't be another expansion of SC2 but what exactly would that even gain? Blizzard can't make campaigns faster than people play through them and that's not even the real game. New units? There's only so much you can add to a game like this and SC2 isn't some kind of MMO that needs perpetual updates to stay interesting. Blizzard doesn't need to make big bucks from a game to keep it running as they've shown with all their previous games (Diablo 2 bnet is still up 14 years later and I believe Diablo 1 and SC too, but I haven't checked in a while), so what exactly do you want them to do that they haven't done already?

id naturally rather go down with the ship.

Be prepared for a looong wait then. They'll leave the game as balanced as they can, just as they did with SC:BW and probably release compatibility patches for new OSes and the servers will stay up for at least another decade, most likely longer. Popularity will naturally decrease, but it'll be quite long before you can't find someone to queue against and at that point the next game in the series will probably be out.