In 2014, Scalia with Roberts, Thomas, and Alito argued that Trump's desired recess appointments are unconstitutional

The decision in NLRB v. Noel Canning, was unanimous in striking down certain recess appointments made by President Obama as unconstitutional.

Scalia wrote a concurrence, joined by the other conservatives (minus Kennedy), that argued the decision did not go far enough:

"that recess appointments will remain a powerful weapon in the President's arsenal. ... That is unfortunate, because the recess appointment power is an anachronism." Scalia argues that the recess appointment power only applies to vacancies that arise while the Senate is in recess.

Under this reasoning, even if Trump succeeded in forcing both chambers into recess, if the vacancies did not occur during that recess, any appointments would be unconstitutional.

It will be interesting to see if they can twist themselves out of this argument for Trump. But such a case would definitely be barreling toward the Supreme Court.