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.