current rumors point to there not being any "pro" model comeing.
Theres a shrunk chip version, that has like 80%+ better battery life, due to shrunk chip + more effecient ram.
That will just be a straight up improvement on the normal model.... and will likely stay at 299$.
I think it more likely that in 2021-2022, there will be a Switch 2 model (thats also backwards compatabile with switch 1 games).