Well if there is no election Trump would remain in office until the election and win four more years from that date.
I suspect D’rats will push electronic voting, so they can steal it.
Trump and Pence’s current terms expire on Jan 20th whether there is an election or not.
House terms expire Jan 3rd, as do terms for a third of the Senators, Governors, whatever are still in office on Jan 3rd can fill the vacant seats I guess.
So Acting President would be a fight between the Pres Pro Tem of a possibly Rat majority mystery Senate and Pompeo, the Sec of State. Without a House there could be no legislation passed.