If it's a large project with a lot of time and money involved they should wait for whatever Wizards says.I think this specific question is best detached from the more general threads.
I have a friend with a team of writers working on a big 3PP Kickstarter/publication, planned to be for 5e using the OGL. She and the team, with my advice, are now working on a non-OGL version. But I suggested that before doing too much work on this - it will be a lot of work - she wait to see if WoTC makes an announcement reassuring 3PPs that they are not trying to revoke OGL 1.0. I suggested waiting until Monday 16th before pressing forward. But I wanted to see what other people think. How long should the community wait on WoTC to speak? Or should we not be waiting? A lot of people already seem set on abandoning the OGL, just from the threat that's been raised.
Especially if it's a first time go at this. When Critical Role does non-D&D viewership shrinks. When an indie with an established name does D&D stuff their numbers explode (see Level up v WOIN).
D&D is still the largest market, by far.
Waiting for a chance that Wizards backtracks means waiting for a chance to grab onto what remains of that market, which will still be the largest even if it shrinks, especially since 3pp are fracturing rather than unifying.
Your friends are risking money. The safest thing to do is wait. The emotional thing to do is rush. They don't have to copy the big players because there's no need for vengeance.