There are rumors that the next step is a TSLA-SPCX merger. Each company has something that Elon wants but is hard to get: Elon has super-voting controlling shares of SPCX, but TSLA is part of the S&P500.

Once a company is listed, exchange rules prohibit adding super-voting shares, it has to be done prior to listing. In order to qualify for the S&P500 a company has to have a large enough market cap and be net profitable over an entire year in the market. It seems unlikely that SPCX will qualify for that bar in the foreseeable future.

However, a merger can combine both features into one company. TSLA recently rechartered in Texas, which makes it very hard for shareholders to sue. Presumably most of the TSLA shareholders today like Elon Musk, so they would be okay with the merger, and as mentioned above Elon has full control over SPCX. Since they are in totally different markets it is hard to see what sorts of anti-trust arguments even a hostile government (e.g. Europe or Democratic state level AG's) could convince a judge of. But he does kinda need the merger to seem like something of equal companies, not an acquisition of a failing company by a successful one, so that he can keep both of the features that he wants.