SpaceX feels like the next "big thing"... question is when does it IPO. Even if the Mars stuff never pans out they can be a very successful business in telecommunication infra.
Gwynne Shotwell has said they could spinoff Starlink as its own company and IPO it and use that money to fund more Mars projects if they run out of money. But if Starlink is profitable once it is up and running why would they sell it off/IPO? Just keep taking the money over years probably will work better in the long term.
I believe Musk would prefer faster returns to speed that up than wait a few years more patiently.