We don’t have that now. Makes no difference whatsoever. There’s nothing left they can take away from OGL publishers!At worst, 3PPs might miss out on access to official D&D branding, IP access, maybe eventually VTT integration or something
The problem with DMs Guild — and I speak from experience of publishing through several edition changes — is that pre-OneD&D material sales will drop off a cliff. Even if they are technically still compatible (as in 3E-3.5) people won’t buy it if it wasn’t made specifically for the current edition. Been there, done that!I strongly doubt it. They'd only do something like that if they thought it would be more profitable than the status quo, and I just don't see where they think this would benefit them. The OGL legal language is pretty ironclad. They're not going to be able to get out of that. Unless OneD&D is way more distinct from 5e, people will be easily able to write stuff under the current OGL that can be used for OneD&D. The DMs Guild is basically just free money for WotC. All they really have to do is sit back and collects their cut. I guess they could be trying to push more people into publishing their stuff through DMs Guild as opposed to freely under the OGL, but I don't see the reward there as being worth the hit to goodwill they would take from fighting OGL creators.
Best adventure I ran for 5E was third party.
Me too. By a looong way. Then again, I published it.Best adventure I ran for 5E was third party.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.