Harry Joe at Margin of Error runs the numbers:
With current polling in conjunction with Bafumi et al.'s paper predicting a Republican national vote between 53.6% and 54.7%, the Republicans could easily gain 50-60 seats from their current 178. Gains of greater than 60 seats also look quite possible. Even in the best case scenario for the Democrats, it would seem that holding the House would be very, very difficult.
(Hat tip: Chait)