Payton said after the game that it would have been Siemian even if Hill was active for this game. But next week it would be Hill. I'm sure he means assuming that Hill is healthy.
Payton did NOT say Hill would be starting next week, just that if Hill hadn’t been injured Siemian would have been backup and Hill would’ve started the next week.
That’s what will happen if Hill is healthy. No way Siemian starts over Hill. Hill was second to Winston this off-season, and nothing has changed. (The thoughts in this paragraph are mine, not Payton’s.)