Possibly 2020, however that will depend whether Inslee runs again, and who the GOP nominates. I will say by 2032 but who knows. The problem for the GOP is Governors elections are held in Presidential years, and the electorate is so polarized that it is difficult to get large swings.
That's a good point about WA governor elections being held in Presidential election years.
Concerning the two sort of recent governor elections then: do you all think Rossi could have beat Gregoire, and could McKenna have beat Inslee if those contests weren't in Presidential election years?