I think the Dems take the House. Some system-shocking event could keep it from happening (or, in the other direction, make it a tsunami) but I think it's nearly inevitable. The healthy economy may keep it from being a historic blowout, but it's going to be a pretty big hit. Senate is another story. Ds have too much to defend and not enough to attack.
The next two years are going to be a lot like the Clinton years. Nonstop hearings and investigations. The chairs of the Oversight and Judiciary committees are going to be on TV more than Big Bang Theory reruns. At some point a Clinton-esque scandal fatigue may set in, but it wasn't until WJC's second term that it really mattered. Trump's not going to have that luxury. Trump is either going to go full Clinton (defend against political attacks but triangulate on policy) or stay the full Trump course, which is likely to end in a smoking crater.