The people who bay loudest about that second amendment have long signaled that they will kill to keep Trump in power. They've been salivating for an excuse to shoot democrats for decades. They have been openly advocating for the murder of democrats for ages. Democrat politicians were literally murdered in the past few years and they don't give a fuck, because they support it.
Trump is already well beyond the confines of the Constitution. If the 2A crowd gave a fuck about rights other than larping soldiers, they would have already marched on him. He has openly declared that guns should be taken away from people and that having a gun on you at a protest should justify shooting you. The 2A crowd continues to support him fully.
The standard dictatorial takeover of a democracy is to keep the elections and the presidency, but to add a supreme leader above the president, similar to what Iran or Russia or China is doing. So Trump would no longer be president, he would be supreme leader joining what the other world powers are doing.