Well, those closest to the grim reaper are mccain and corker. Corker already retired, and a special election will be held this fall for the remainder of his term I believe. Mccain is still with us, but it is doubtful he will return to vote no matter how important the vote is.
So the effective vote balance is 49-50 until mccain either retires or leaves another way. If we can get one more seat, it will be 50-49 if mcain doesn't come back to vote. We wouldn't get control of the leadership, but we could stop any bad nominations a least. Thats if dems stick together, which is always a challenge.
On the red side, the following states have senate elections: Arizona, 2 in Missippi, Missouri, Montana, Nebraska, Nevada, T,N texas, utah, and wyoming. Republicans are still strong favorites in every one of those races except Nevada, which is D+1.
The dems on other hand, have several seats open where the R's are favored: FL, IN, MO, MT, ND, OH, and WV. Those are all R+2-R+20.
So we have a shot at maybe 1 or 2 pickups, but they have a shot 7. It would have to be one hell of a sea change to move those states and get them over the finish line. It has to overcome dirty tricks, election fraud, massive amounts of money puring in from domestic and foreign sources, and the basic instincts of the voters in those states.