Personally, I would say lean R.
The senate map at face value is more favorable to Democrats than not, but it'll be hard for them to get a midterm without a terrible national environment. Also; please don't compare this map to 2018 senate map; in 2018, Rs had low hanging fruit in deep R states, all the states with R incumbents in this map have an even PVI at best.
With that being said, both sides definately have several realistic pick up opportunities and anything from 52D-48R to 56R-44D seems pretty realistic, especially considering all the uncertainty this far out.
My overall map, many seats that should be safe are likely out of caution:
https://www.yapms.com/app/?m=4ynp