For Congress, I think that the breakdown will be:
Senate – 50 Republicans, 50 Democrats
House – 240 Republicans, 195 Democrats
My reasoning? I just took FiveThirtyEight’s numbers and shaded them a bit to the Republican side. There’s no point in making predictions unless you predict something novel and a bit off expectations. Additionally, since the readership here leans a little Left I am inclined to tweak you guys a bit and make the political Götterdämmerung even more terrifying, though I didn’t want to push my luck and give you an implausible value which you’d reject on the face of it.
Image Credit: Therealbs2002, Wikimedia Commons