Nothing will happen Tesla is already profitable with out carbon credits in each car they sell.
Tesla sell carbon credits to companies that need them and they will always have a market for them,it's real money not from the government.
They are able to use this money to build more giga factories, invest in technology and grow the company hence why the carbon credit was set up, unless every company in the world is going to be carbon neutral this decade Tesla can keep using its income to reinvest and dominant.
As for the internal combustion engine car maker's they are cannibalising there own ice vehicles to try and catch up to Tesla who are moving further and further ahead.