I doubt Scott wins 2016, but he'll have a very good chance in 2018. Especially if he runs a respectable margin in 2016.
He can win even in 2016.. Vermpnt voters are flexible and quite adept at splitting their vote. After all - he rather easily won Lt. Governor election in 2012 despite big Obama win in the state, and Democrats will have rather late (August) and, possibly, divisive, primary in 2016..
But Vermont has not elected a non-incumbent Republican governor in a presidential year since 1976, when it hadn't fully trended Democratic yet. Richard Snelling and Jim Douglas were elected in midterm years. I think it will be difficult for any Republican to take the governorship in a presidential year-even an established winner like Scott.