The browser is one of the only truly cross platform development environments around. The popularity of the browser is directly coupled to that fact in my opinion. How many developers|companies and organizations would be over the moon excited with hiring a Python|Ruby|Lua|Rust|C# developer that could talk natively to the browser? My guess is a LOT.
On the other hand, "keep up with JS" is something of a misnomer here. It's not javascript that's moving super-fast, it's the web ecosystem (plus the node one, in parallel). It's moving fast because new ideas are evolving at speed (functional-reactive approaches, new ways to think about mixins vs multiple inheritance, etc), and those ideas lead to new framework architectures gaining popularity as they exploit these new ways of thinking about organizing data flow through a complicated system.
Couple that with some baseline things that aren't changing here - you're still going to have to interact with the DOM, you aren't going to magically get re-entrant multithreading, and the event model isn't changing. There's still going to be a lot about web programming that feels different from systems programming, and things are still going to move quickly. Probably even more quickly (but I'm not certain about that - I imagine one major reason JS shifts quickly is that it has so many programmers working with it, if the population fragments there will probably be a number of slow-moving communities that neither shift often nor take advantage of new features, which feels like the kind of neophile - neophobe split that's already apparent in different areas of programming).
So: I am not convinced that a (say) rust or go compiler to WASM will suddenly make front-end programming feel like systems programming. It'll be a new language, sure, but there's a lot more to web development and the (reasonable) complaints people have about a shifting landscape than just javascript and its funky definition of OO and triple equals sign.
Paralyzation due to choice and only so much time to evaluate each framework. Couple that to "staying" power, that is, will this library be around in 6 months? I have taken a peek from time to time and been thoroughly aghast at the volume and not really seeing any of the old stand-bys around.
Now compare that to Python. There is no dearth of choice and one will find many of these choices have been around for more than a decade. They have evolved and changed of course, but not anywhere near the pace of JS. Again, I could take a 3 to 6 month break from looking at Python news and libraries... then come back and jump right into most of the libs I already know. Can a JS dev do that?
> Couple that with some baseline things that aren't changing here
Doesn't webASM give the power to abstract those things away? React creates a virtual DOM, right? Why can't Python create a virtual DOM via webASM?
I stand with you in that I agree things are going to move quickly once Python and others become peers with JS in the browser. I am sure it will be insane as everyone figures out which lib will have staying power like Django, or similar in another lang. I do think that people who generally gravitate toward languages like Python, Go, C#, Java will bring those attitudes with them... that is, they aren't going to re-invent the wheel every three months unless there is a super compelling reason to do so.
I think, though, that you could pretty easily take a break from JS dev and come back and still use the tools you had six or twelve months ago, just fine. For example, I maintain a pretty big angular 1 application that has a lot of pre-1.4 code in it. It runs fine, and I haven't touched my build tooling in over a year. There's still a lot of very relevant questions and answers on stackoverflow and so on.
Now, I may well want to use react or angular4 or something else for my next project, but nothing is stopping me from using angular 1, or backbone, or just plain jquery for that matter. They all still work.
As to the virtual DOM - abstraction libraries are really cool (although the vDOM isn't really that), but they introduce just yet another thing that changes over time. At the end of the day, the DOM is a pretty complicated thing, between its own structure, event models, css, and everything else, so the API to interact with it is going to be complicated no matter what language you use. Most frameworks (backbone, jquery, angular, react, etc) are all just different attempts to manage that complication, and all they ever really do is shove the complication from one place to another, but (for example with functional reactive models) that other place is something a group of people is willing to deal with.
