It is unclear how much the lame-duck Congress will accomplish in the last legislative days of the 115th Congress. Funding does run out for Homeland Security and the Justice Department and there will need to be some extension. There are hopes that funding will be completed through the end of the fiscal year on September 30, 2019 but that could be complicated.
There has been talk of giving the President $5 billion in wall funding but that would require at least some Senate Democrats to not filibuster such a deal. The election defeat of some vulnerable Senate Democrats would give those senators a free vote against such a proposal without any concern about opposing the President. A Justice Department budget will also likely include efforts to protect Special Counsel Robert Muller from ouster.
Beyond the specific issues in funding is how much will House Republicans being interested in remaining in town to back up the President. Before the election, 54 Republicans were retiring or running for another office, in addition 20 or more Republicans seeking reelection were defeated. After the President publicly ridiculed some of the members who lost their reelection bids by name and in a very personal way, there are likely to be bad feelings not just by the members he targeted but many of their colleagues who are also friends and sympathetic to losing a tough election.
It is possible they could do a short-term budget into the new year which would mean the President would be forced to deal with a new Congress with a friendly Senate but a House in opposition.