I think Democrats are too disillusioned right now to generate a blue wave. There is no fire or drive, nobody to lead them. Republicans will lose a few seats probably, but it won’t be a wave. If there is going to be a blue wave I think it happens in 2020, 2022 at the latest.
If a person like Ocasio Cortez can win and basically cause a major (almost historical) upset, then I think there's more to it than you think. Hell, you have democrats winning in Alabama. When the time comes, they won't care who runs, as long as it isn't someone from the republicans/trump camp.