Something about Endeavor I never knew is that they've been running the WWE Network for the last 4 years now through Endeavor Streaming.
So now them owning WWE hopefully doesn't change much about the network since their technology is already driving the network.
I don't think they should ever have a combined WWE/UFC event. Many UFC fans hate WWE don't they (even though they were probably former WWE fans).
If they have a new streaming service, maybe it works similar to the other ones. It's not a single network for WWE and UFC, but it'll be a service where you can subscribe separately or together.
Let's say each company is $10 a month for their part of the service. If you sign up for both, it ends up being $15.
If they do a combined weekend, I hope WWE keeps the Saturday night PLE slot and UFC happens in the same venue on the Sunday.