The way to unblock the filibuster is for Trump to nominate Garland and for the Senate to confirm him.
The president in power gets the next nomination.
You can't cheat the way the Republicans did and expect the Democrats to play fair.
If the Republicans remove filibuster rules, so be it. I guess Democratic justices will hold on for the next president. If they can.
Another solution would be to max out the period that a person can sit on the Supreme Court. 18 years (4 1/2 presidential terms) sounds long enough.