Hard to predict. I'd be surprised if there is a significant gain for either party in either house. Historically, minority party gains votes when the oposing party is in the White House, but then again, GOP made significant gains in previous 2 elections, and Democrats seem to be as lost as they've ever been.
My best guess is that nobody will gain more than two seats in the Senate nor more than 5 in the House, but 11 months can be an eternity in politics.
"Don't try to threaten me Mulder! I've watched presidents die."
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Cigarette Smoking Man