The Senate before the election
Composition is 26 Republican seats, 22 Democrat seats. Now for the next map:
The Senate after the election
Composition is now 32 Republicans, and 16 Democrats. The next map:
In 2012, 24 seats are up for grabs: 15 Republican-held and 9 Democrat-held.
The bad news for the Democrats is that all of those 9 districts are east of I-35 -- and all of the 2010 GOP gains were east of I-35. 9 seats is just over half of the current 16-seat Democrat Senate minority.
Judging from how poorly the Democrats did this cycle, and add to that the fact that Barack Obama will be on the ballot, eastern Oklahoma and "Little Dixie" don't look that secure for the ODP.