So this won't be popular but I think the outcome of the next four games could potentially trigger a "transition" season at QB. Here's my rationale...
First, Stafford is old, he's got hard miles, and he's been butting heads with the Rams the past two offseasons about his contract. He got a new contract in May that will cover him through the 2027 season. He just won the MVP last year. Looking at his performance in the opener, he was overly concerned and affected by the rush, inaccurate due to it, and was benched in the 4th quarter (and rightly so).
Second, the Rams invested a top pick in Simpson. He played well during the preseason, looking very sharp, and because they took him in the first round he comes with 5 years of team control.
Third, the next four games are brutal. The Giants are the "easy" game, and they will be bringing the kind of physicality that always gives McVay teams fits. Then after that game we have @ Broncos, @ Eagles, and Bills. That's a 3/4 playoff level matchup, and it's possible the Giants end up a playoff team this year or at the least a contender for a spot instead of their usual failings.
Where the next four games factor in is that if the Rams end up sub .500 and/or alone in the divisional basement, that may serve as the trigger in utilizing this season as a transition to the new QB. It is when all those elements sort of come together and force the Rams to ask that question. Do you think they won't be thinking about starting the kid if we're sitting at 1-4 or maybe even 2-3? The worse the record of course the more likely it becomes.
And I don't know if Stafford sees this coming. Is he going to recognize the threat of it. I am sure, after all, that he feels quite comfortable with his new contract and coming off the MVP season, where his job security probably isn't a question in his mind. The kid is parked at QB3 as well, and if I were him I wouldn't worry about Bennett either. But the threat is the kid. Where the team will ask that question "why not see what he can do" in the event they find themselves buried in the early season standings. And depending on how they answer the question, that may effectively start the new era at QB a bit earlier than anticipated.