It seems quite likely the Democrats will take the Senate.
So far we have
46 Democrats + 2 Independents (Caucusing with Democrats): 48
Republicans: 49
Control comes down to 3 races: Montana, Missouri, and Virginia
Webb (D) has declared victory in Virginia, but there will be a recount. He seems to have the numbers to maintain his win, though.
McCaskill looks like she will win Missouri, and Tester will win in Montana.
That's 51 for the Democrats, and Senate control.