Where do they play?
NBA would not go away. A 30-team new league would not crop up overnight. There won't be universal support for the new league and that kind of infrastructure can't come together in <1 year. The NBA owners sure as hell aren't going to go quietly into the night and share the arenas. You can bet there are non-compete clauses preventing ANY basketball team whether pro or minor-league from playing in an arena without consent of the NBA team(s) which have leased that arena. Of course SLC is unique because the team owns the ESA. So a new league is relegated to either playing in college arenas, cities without pro franchises (but with existing "NBA-ready" arenas) or abandoned arenas (e.g. the Forum, Key Arena, etc.).
So let's assume LBJ can convince 100 or so players to defect with him and form a new league. Ten teams in LA (likely playing in Anaheim), New York (maybe playing in New Jersey), Seattle, Nashville, Las Vegas, etc.
Now what? Revenue is not going to be anywhere near what teams in the NBA generate. Gate receipts, broadcast or streaming deal, sponsorships, merchandising, etc. will all be much, much smaller with the major players wanting more of it. So do these players go out and try to find the most idiotic billionaires on the planet to own the teams? Hey, we have an incredibly risky business model for you to invest in, and oh yeah, most of the profit goes to us. Or they sell shares? Again, investors want to see solid returns on their money...the riskier the investment, the greater the expected return.
The NBA would survive with maybe 4-5 small market teams going under. The new league would last 3-4 years tops. The stars might still make good money initially, but every other player would see they could make more in the NBA and BEG for reinstatement. And this won't be a situation like the ABA; there would be no merger.