It all comes down to opportunity. If Joe re-signs Calderon and manages to get a good deal on a second tier player (like Redick), there's nothing to stop us from benching him. Overall, Knight hasn't just been disappointing, he's been really bad. It wouldn't take a great player to replace him in the starting lineup. SF is only a slightly greater need than SG. Knight and Stuckey were failures at the 2, just as Singler is not a starting caliber 3. We could improve the team by equal measure getting a good player at either spot.
Consider the players available in FA and the draft. If someone like Oladipo is still on the board, we take him and start him. If someone like Burke, we take him and hope Knight/Stuckey improve. If we land Redick or Mayo (I hope not, but Joe seems to enjoy overpaying undersized, overrate guards), we put Knight on the bench.
I don't think it's expressed enough, but Knight hasn't been any good. Part of his projection as a bench player stems from the fact that he's just not done anything well as a starter. The team may choose to bank on his development because they have no other options, but he wouldn't be starting for ANY other team in the league right now. If we go into next year with Knight as our starting PG or SG, it will be an indictment of our overall talent.