Considering Snyder won by 18 points in 2010 yet is now in a real race (and Peters looks set to win by high single digits/low double digits), if there does end up being a wave, it probably won't be washing up on the shore of Michigan.
The Democrat running for US Senate is going to win by double-digits, too. The most likely scenario in Michigan is that--just as in 2012--absolutely nothing changes. None of the US House seats flip, the Governorship doesn't flip, the GOP holds the State Legislature, AG and SOS offices, and Democrats hold the US Senate seat.