We're about to see a shit-ton of legislative filibusters. The Democrats will hold up every piece Trump's agenda. Democrats will claim they are resisting Trump, Republicans will claim Democrats are being obstructionists. Same old politics as usual.
The problem is that the Democrats don't have much to lose, they don't control either chamber and will most likely emerge from the 2018 midterm with enough seats to continue filibustering everything. The Republicans on the other hand got elected on certain promises (repeal Obamacare, tax reform, border wall, etc), and now all of them are effectively dead on arrival in the Senate. If Republicans can't give their base something to come out for in November 2018, they stand to lose a number of seats in the House. The Democrats need to gain 24 seats to win a majority. Its a long shot, but larger swings have happened before and if Trump remains this unpopular, such a swing becomes more likely.
This puts McConnell in a tight spot, there are a lot of programs which Democrats have been pushing for that a) Republicans strongly oppose and b) will be almost impossible to repeal once implemented. Think single-payer healthcare, amnesty, free college tuition, etc. McConnell's not an idiot, he knows that politics goes in cycles and that the Democrats will one day hold the majority. If the filibuster goes away, all of those programs will be implemented and his party will be powerless to stop them. One the other hand, if he keeps the filibuster around, literally nothing will be accomplished for the next few years.