LA will be "car-free" for the Olympics. For definitions of "car-free" which include crippling car traffic everywhere except tiny islands around a few select locations. Said locations being strategically placed to make the crippling traffic worse everywhere else. And once it's all over, everything which was built out will be allowed to fall into disuse and disrepair. As is the Olympic Tradition. But, at least, a bunch of large companies will make a lot of money, with all of the expenses covered by California and LA tax payers. Again, in the best Olympic Tradition.
That proposal by Musk was so bad that it is possible that it was a move to impede/prevent the rail-project california had planned by proposing a "better" idea.
In four years? This is the same guy who said we'd be colonizing Mars in 2025 after launching a starship voyage in 2022. The same guy who for 10 years has been saying self driving car features are less than a year away.