Some have speculated that the U.S Congress may move to extend the EV tax credit past the current limit of 200,000 U.S. sales per auto maker, so that GM and Tesla can continue to benefit from the tax rebate.
But that ignores the fact that far-right hardliners in the GOP are now in control of Congress. I think it far more likely that they will move to cut off the EV tax rebate as soon as both GM and Tesla cross the limit of 200,000 U.S. sales. There are certainly good reasons to believe that may happen; in fact, I'm surprised that the GOP-controlled Congress hasn't already moved to eliminate the EV tax credit altogether, given how pro-Big Oil Trump's original cabinet was, and how much the Scott Pruitt-lead EPA is rolling back and weakening restrictions on air and water pollution, as well as rolling back and/or weakening the mandate for automobile emissions.
Make no mistake: The Trumpster administration is, in general, strongly pro-Big Oil and anti-"green". That doesn't necessarily mean that the Cheeto-in-Chief himself is anti-Tesla, because it is a company making American cars. But it's the GOP in Congress who will decide whether or not the EV tax credit gets extended or, alternatively, gets cut off sooner than originally planned. The Big Cheeto isn't likely to try to influence Congress on that decision. Even if he's aware of the issue (which I think unlikely, given the fact that he reads almost nothing other than Twitter posts), I seriously doubt he cares much either way, let alone care enough to try to use his political influence to affect the outcome.
Contrariwise, the hard-liners in the GOP are very much opposed to EVs in general. Let's not forget that GOP presidential candidate Romney once called Tesla one of President Obama's "failures" during a debate with that President. Of course that's laughable -- nearly every company in the world would love to be as much of a "failure" as Tesla! But it certainly shows the hostility that GOP politicians -- especially far-right GOP politicians -- have toward Tesla and EVs in general.
If Congress does move to change the rules for the EV tax rebate, that will likely happen not long after either GM or Tesla crosses that 200,000 milestone. That will almost certainly happen to Tesla this quarter -- that is, sometime before the end of June this year. I'm not sure when GM will cross the threshold, but from what I've read it will happen at close to the same time, perhaps in the same quarter.
Contrariwise, given how difficult it has become for Congress to pass any bill at all of substance, it's quite possible that no change will happen. In that case, Tesla will see its tax rebate drop to half at the end of the 3rd quarter this year, and likely GM will be at the same place or not far behind.
Meanwhile, the other auto makers will unfortunately be rewarded for their foot-dragging on marketing EVs in the USA. It will be years before they pass the 200,000 threshold, so they will continue to benefit from the tax rebate for years unless Congress moves to change the law, while Tesla and GM get punished for actually taking the lead in building EVs to sell in the USA.