Well, this isn't framed as a buyout/takeover, so I was curious how existing RSUs would be cashed out?

This deal is framed as IP transfer and talent transfer without owning the full company. Probably to skirt anti trust, among other things.

I'm not sure in this specific case. They could choose to pay the employees some portion of the funds.

If not, the owners are likely liable to be sued for "selling in effect" without paying equity holders.

Presuming the company becomes a defacto subsidiary of Nvidia (even if not legally so)

My guess, without researching it, is they will compensate existing equity holders to avoid that possibility. I mean the valuation multiple is enormous, it's worth it simply to derisk the legal aspect.

For vested RSUs it's likely that the Groq husk will pay out the $20B as a dividend or buyback or something. I don't know if unvested RSUs are accelerated or just canceled. Of course the employees will receive new RSUs when they join Nvidia.