Donald Trump suggests delay to 2020 US presidential election
It's not going to happen because the Democratic-controlled House would have to agree, and they won't.
The real wild-card is Republican-controlled state legislatures, which have the Constitutional authority to cancel the Presidential election in their state and choose the electors themselves. The bad news for Democrats is that every potential swing state has a Republican-controlled legislature (AZ, FL, IA, MI, NC, OH, PA, TX, WI).
If the election were held today, and the polls were mostly right, Biden would win with 319-219 electoral votes. (That's being cautious and giving NC and TX to Trump despite Biden's current slim lead in each state.) If each of those likely Democratic-voting swing states' Republican legislatures decided to submit their own slate of electors in favor of Trump, Trump would win 305-223.
But wait, there's more! Because each state has laws governing the election, the legislatures of those states would probably have to change state law to submit their own slate, not simply vote for their own slate. That's an open question, I think, but if a legislature tried to simply submit their slate without providing for an exception to the law, they'd would certainty get tied up in court very quickly by the Democratic Party and Democratic voters. So if state law must be changed, then that makes the state governors relevant.
Four of those swing states have Democratic governors (MI, NC, PA, WI). If the Governor in each of those states stopped a legislative attempt at changing election laws (and in every other swing state the GOP controlled legislatures succeeded) AND Biden won each of those states except NC (as assumed above), Biden would win 279-259.
But what if the legislatures in MI, PA, and WI overrode their governors' vetos? In each state a veto override requires a 2/3 majority in each chamber, and the Republicans don't have the numbers in any of those states.
So it's unlikely that even such a radical -- but constitutional -- move by Republicans could swing the election to Trump.