Musk doesn’t seem particularly good at lawsuits. Remember when he was suing Twitter to get out of having to buy them?

Perhaps he lacks good lawyers, perhaps he just can’t find substance and he’s filling out of spite.

That's misunderstanding the finances involved here. OpenAI is a privately held company; sure, that means they're "borrowing" from their investors technically. But that's in exactly the same sense that a public company is actually "owned" by its shareholders. The behavioral relationship goes the other way: people own bits of the company because they want it to do well and their share to grow in size, not because they expect the debt/dividend to be repaid per se.

In point of fact most valuations place OpenAI in the hundreds of billions of dollars already and growing rapidly.

Basically, no: OpenAI's pockets are deeper than Musks's personal wealth. Especially so considering that this suit is existentially important to them where Musk needs to maintain leverage for other efforts.

There won't be a round 2. It's over.