Just checked: the income limitations is for the State of California credits: there is no income limitations for the Federal Tax credit. The full $7,500 Federal Tax Credit will be available for all 2021 MachE.
The income limitations may be unique for California: 48% of all Tesla were registered in California and California was taking a hit with the state rebates going to the very wealthy.
BTW, without getting into the politics, the Senator from Wyoming wanted the $7,500 credit repealed, as it was "going to wealthy Californians buying $100,000 Teslas who would have bought the cars with or without the $7,500 rebate" (paraphased)
In New York where I live, in addition to the $7,500 Federal Tax Credit there is a $2,000 State tax credit with no income limitations. So the net cost of my First Edition will be about $51,000 less X-Plan savings.
Again, as I posted above, this is a credit and is applied to your taxes due: so to take advantage of the full $7,500 you must have a tax liability of least $7,500.
You can google $7,500 EV credit and there are many articles that explain how the tax credit works and the IRS forms you fill out.
Finally, the tax credit is for the year you register the car: it is not the year you buy or place an order for the car but the year it is registered. IRS considers the year you register the year the car is put into service.
Hopes this clarifies.