I really don't think they are going to trade up. I don't think a deal is in the works for Foles at this point in time. I don't think they want to eff around with a rookie when their jobs are on the line. The only QB that will hit the ground running is Lawrence (maybe Fields on the right team, not the Bears with Nagy), everyone else is a project - they don't have time for projects, that was Mitch.
Both QBs have a career 87 rating. If one guy gets injured another vet steps in. Neither are very mobile. This seems to be what Nagy wants.
The best thing here is if Nagy makes two average QBs worse - there's no reason not to fire him. He couldn't develop Mitch, Foles regressed to an 80 rating, if Dalton regresses far past an 85 rating - bye bye Nagy. (I have no doubt o-line upgrades are coming, so there's no o-line excuse either.)