Nitpicking: Actually, we can. ES6 modules are supported by browsers for 93.38% of all users now:
https://caniuse.com/es6-module
A typical phoenix (LV or not) application only have a handful of js files. I don’t bother to bundle or minimize them any more. Granted if the user want to do something more complex they would need to pick a toolchain, however, by then the user should be sophisticate enough to pick on their own.
We very much explored this route, and this was my initial take on the matter when we decided enough was enough wrt to placing the burden of node on phx.new users. The “simply use <script type=module|modulemap and let HTTP2 take care of it, which no build step at all” was very much explored. Unfortunately, I don’t think this is the best default today as any moderately complex LiveView app doing its best to avoid javascript will still necessarily have more than a handful of js files over time. Charting, stripe/payments, alpine, hook files, etc. For example, livebook has 30 js files today. HTTP2 is great, but making dozen of H2 requests for assets isn’t a long term ideal solution. This is of course a great option for folks who truly have only a handful of js files that don’t creep over time, so by all means go for it! 
Yeah eex can be used for so many other things, like xml, graphql, programming languages, etc.
I’ve also got at least one index.xml.eex file in just about every project I use. Hopefully .eex template support isn’t dropped from Phoenix, even if .eex disappears from the generators.
That said, I’m super excited about this release!
In particular, the move away from NPM and Webpack to esbuild is something I was already playing around with and considering on my own. I was worried about a lack of searchability given the intersection of Phoenix users and esbuild users being too small. Bringing it into phx 1.6 completely solves that issue 
Ah, so it is!
I’ve used it outside of Phoenix myself a few years back, but having done every web project in Phoenix for the past few years, I’d completely forgotten.
So, most people feel the release is 1 month away. I voted for <1 week. Let us wait for the actual results.