What if he comes back, but his powers change from the speedforce to the bleed?
It would make some sense for that to happen as the speedforce is adjacent to the bleed as well as the dream. So let's say that Wally tried to escape Convergence but wasn't quite fast enough and got caught in the bleed with Braniac.
That would allow them to sort of go back and claim that Wally was instrumental in Braniacs defeat and has been keeping him in check, in the bleed ever since.
It would also allow him to keep a similar yet different powerset as he could move in between or outside dimensions instead of with the power of the speedforce, sort of like Zolomon using time instead of speedforce.
It would also satisfy Johns whole crush on Barry being the greatest/primary speedforce user and whatnot.