I am not forgetting anything. The 3D VTT is a different beast entirely, aimed a different audience, designed for a different (monetization) purpose. Beyond Maps is intended to bring people to Beyond, and to do that it HAS to be better than VTTs where you can already leverage Beyond to use the VTT -- specifically, Roll20.
No. It really doesn't. WotC would be happy if you use Roll20, Fantasy Grounds, or Foundry and buy their official content for these platforms.
If they live up to their marketing, their official VTT will still support flat maps and will have the best automation for the official rules with some options for optional and homebrew rules. It will directly compete with the other major VTT platforms. The main thing that it won't do is support non-DnD systems. Which is why they are still licensing official content for purchase through competing VTT platforms.
I predict that Maps will have the most users among DnD players. People who want a simple flat, battlemap that is well-integrated with DDB's encounter building and character sheets.
The WotC VTT (is there an official name for it yet?) will be for DMs with the disposable income and interest in a full featured VTT with the best support for the official rules, and who appreciate the more video-game-like 3D presentation and automations.
Foundry will be the for the tinkerers and customizers. I don't see any other VTT that is close to having the modding community that Foundry does.
Roll20 will be for those who want support for a variety of systems but don't want to deal with having to install software, configuring network connections, and have access to healthy marketplace of content and a large community for finding campaigns and one-shots to join.
Fantasy Grounds...I think they are at the most risk of losing market share. I'm not sure what their niche is. One thing I think FG does well is in-house official support for suppored systems that do a good job at automating things. It is also perhaps the best VTT for those who want to both play remote and in-person games using a VTT. But the fact that all players have to install software and the high learning curve increasingly makes it a hard sell. Also a lot of people find the interface outdated and unintuitive (I don't mind it myself). In my experience, its customer base is more people who have been using it a long time and are invested in it. I don't see many people switching to it from other VTTs and see very few people choosing it as their first VTT.
d20pro. It is still around, I just never see it in the wild any more. I can't think of any reason to choose it over other offerings.
Then we get to a long tail of other VTTs that have their fans but I don't see winning a significant share of the VTT market.