The slickly redesigned Cook Political Report is saying that the Republicans are likely to pick up between seven and nine Senate seats in November, with an outside shot at getting the 10 they need for a majority:

The macro political landscape strongly favors Republicans and it is not likely that it will change much between now and November. As a result, a look at the 37 Senate races on the ballot shows some deterioration for Democrats in some of the 19 seats they are defending, while Republicans’ prospects have stayed the same or improved slightly in their most competitive seats. As such, it is now likely that Republicans will score a net gain of between seven and nine seats. While there is a plausible argument for how Republicans could net the 10 seats they need to win the majority, it remains an unlikely scenario today.