Cook Political Report's "Bottom Line":
Given the national political environment and that the Senate race map favors Republicans, it’s not hard to see how they get the six seats they need to win the majority. At the same time, the known unknowns like run-offs and the Democrats’ ground game, make it easy to see how they could fall just short. Overall, we tend to believe that Republicans will get to 51 seats.
My guess is 52, even with Roberts being bumped by Orman. So, depending on Orman's caucusing decision, I'm guessing it could be 53. But of course we still won't know the outcome by next Wednesday, given the very high chance of a runoff or two.