I think I would be incredibly disappointed if some of the stretch goals were discarded. Probably mostly because stretch goals are an implicit promise of sorts. KSers and PP backers often specifically donate more because they want to see these things in the game. They expect that if they put out extra funds they'll get to see some of those extra features although I hope we all understand that developing anything on a large scale is a financial risk. Costs change, some features don't pan out the way they're conceived in the planning stage (not fun, feasible, practical), and time constraints interfere. We can hope that everything was properly evaluated in advance to reduce waste and loss of any features anyone was anticipating but at the very least, if there's no other choice but to start cutting content, we should have a voice in which content gets cut.
But we should have faith, the team seems to have an impressive track record and they've been very transparent and open with us so far.