So apparently there's a chance he may not run for reelection to the State Senate next year in order to focus on a likely 2022 congressional run:
https://www.politico.com/newjerseyplaybookHis district was solidly Republican at the start of the decade. Trump is anathema here, although they are still willing to vote for the right downballot Republicans (Kean himself in 2017, Bramnick and Munoz). I guess we need to wait and see what happens. New Jersey will be the first real test of the post-Trump GOP.