Then again it is possible and Chris Cao did do Magic Arena. So we'll see.
So Magic has a virtual tabletop system, it's called Magic Online. It's old. It's buggy. But it does exactly what it says on the tin; you can play Magic against anyone in any format online. You can buy singles, make decks, play anything from vintage to standard to 4 person commander. You can sell your decks and even "cash out" and request paper copies of any complete set. (Or, you could). In short, it handled everything you can do tabletop. You could even buy and play Black Lotus because the reserve list didn't apply to digital cards
Also, Magic has Arena. It's newer and slicker. Pretty graphical flourishes, etc. And it has a bunch of things you can't do that you can do with Online. You can only play one opponent at a time. You can't play commander. You are limited to only sets from the last few years (so much so, you can't play it's most recent legacy format Pioneer, but can play a bastardized version called Historic). They have changed cards, effectively errataing them (called Alchemy) and have cards with mechanics that would be impossible to do in paper Magic. You can buy wildcards and packs, but you can't buy and sell individual cards. It's very much designed to play Magic, but not emulate playing Magic, as online was.
D&D Beyond, in its current format, feels a little more like Magic Online. It's designed to assist and emulate tabletop D&D. So far, there is nothing you can do on it that you can't do with a pen and paper. But what if the vtt is like Arena; a curated experience not designed to strictly emulate the TT experience but provide a similar, highly controlled and monetized one. It's designed for players who want to use official rules to play official modules with other players (groups or random) against a DM who will have all sorts of tools for running that module (including that dreaded AI). A VTT that is designed to play D&D, but not to emulate playing D&D.
Also, since we're talking about a separate experience, it will have limited integration with Beyond. After all, buying a card on MTGO doesn't get you access to the card on Arena or IRL.
But Cao might actually be a mad lad. Just like how Arena didn't kill competitive Magic, but provided a limited style of play to anyone who has some time to play but not the ability to find a play group, this could do the same for D&D. And Cao could have been upset when he found out Wizards just bought another Magic Online in Beyond to muck up his plans for a single curated online play system.
But the more I think about it, the more D&DB:VTT :: MTGO:Arena makes sense.