We will not know what is Elon plans with those two coins but he has already made a noise in the crypto market so I guess he will make another tweet in the future.
Those two coins now become popular besides bitcoin and ethereum but if we compare with bitcoin and doge payments, I think using bitcoin as the payment will be better.
Maybe we need to wait for the next announcement from Elon or Tesla for what coins they want to use as the payment.
But I do not want to buy Tesla using bitcoin, ethereum, or other coins as crypto will be just my investment.
I hope that he doesn't move to other coins as well because he is making the crypto world a lot fragile with what he has. I get that he is not doing it because he is just happy to do it, he is doing it because he gets love back from doing it plus he makes money from it as well. However just because he could help you make some money, doesn't mean that he wants the best for you neither, he is doing it because it helps him as well, he could literally be doing a lot worse things and still be happy as long as it benefits him.
Doge and Shiba are two things that could crash at any moment, or maybe they will do 2x, nobody knows this and there is absolutely no reason to hold them neither. This is why we should be a lot more careful with them, and him pumping it causes it to be a lot worse, this is why we should be a lot more careful, because him making it viral is dangerous for the future of crypto.