I don't know of any "can't miss" QB prospects coming out next year. The best choice would be to see how the season plays out, draft for O-Line and if you have another **** season, you may at least be in position to pick up a decent QB.
Between Mason and Haskins, I assume they can win a few games and at least keep the lights on. I have no illusions whatsoever that Tomlin can win a playoff game, but honestly, the long term strategy has to be a complete rebuild from the O-line up with an eye on fielding some kind of defense as you waste Watt's career.