And lose a chunk of people that only enjoy Java edition specifically because it's Java edition.

I don't see this happening, for three reasons:

1. Community oldtimers and loyalists really like Java.

2. Bedrock has no Linux port.

3. Java is the lead version - new features are added to it first and then backported to Bedrock.

While #1 and #2 could be written off as "costs of doing business", the latter is a significant problem. The current creative process that Microsoft and Mojang has adopted is that Mojang implements new features and versions in Java first, and then another team in Washington reimplements them in C++ for Bedrock. Deprecating Java means making everyone at Mojang switch development tools and languages and adopt an entirely different codebase. It would be just as disruptive for Mojang as it would be for modders.

I don't disagree with your conclusion, but I do think your information is a bit outdated. In recent updates, effort has been made to keep both editions as much in sync as possible with explicit goals of feature parity and synchronous releases. I don't work at Mojang so I can't speak with complete certainty, but I know there are a number of developers who develop features for both editions simultaneously [0]. That said, all the core developers I've heard from are extremely passionate about the Java edition of the game and have absolutely no plans to stop supporting it. If that ever happens, it will have been a Microsoft decision that they had no say in.

Unfortunately sifting through the last few years of Minecraft.net articles and Minecraft Live footage to find sources isn't a great use of my time right now, but I'm sure it's out there. Bedrock was shifted to the same version numbering system as Java in the last year iirc and they've been releasing snapshots and betas with the same content on the same day for all of the 1.19.3/1.20 snapshots so far and I think the 1.19.0 ones as well.

[0] https://mobile.twitter.com/kingbdogz/status/1509482290304659...