Java - including V8 - is already on ARM: https://bell-sw.com/java/arm/performance/2019/01/15/the-status-of-java-on-arm/
Eclipse and Android Studio are cross-platform IDEs written in Java.
No, that doesn't mean there are ready-to-go downloads of Android Studio, Eclipse and JDK8 for a hypothetical ARM Mac - but it means that producing them would hardly be the Manhattan Project and if there is sufficient interest they will probably appear.
...when you are developing for iOS in XCode, the app is compiled for x86 and run in an iOS-for-x86 sandbox on the Mac, then when you deploy to an iDevice it is re-compiled for ARM. At best, an ARM Mac will be more suited to that job - at worst, you won't notice the difference.
...for Android, you're mostly compiling to processor-independent Dalvik bytecode. If you are writing native code, then most Android devices are ARM so you'll be testing in QEMU or suchlike under software emulation, and working on an ARM machine is going to be far better than that.
...for Docker, maybe you're one of the subset of developers writing C/C++, in which case developing on Docker for ARM makes as much sense as... well... developing for iOS on an x86 Mac. However, a lot of Docker developers are writing primarily in HTML5, Node.JS, Python, PHP, Java which is all processor-independent, and layering this on top of pre-built containers with the necessary software 'stack' (all the usual suspects like Node, Mongo, MySQL, Apache, NGenix are already up and running on ARM Linux). The alternative, of course, is just spinning up a Docker server on a beige box in the server room, or somewhere in the cloud: there's not much difference between using that and a headless VM and most of the Docker tools are network aware. There's some very interesting remote development stuff in Visual Studio Code now that supports docker and remote Linux systems.
There is a lot of interest in ARM (and other architectures) on servers at the moment and significant effort is already being put into Linux on ARM and easily targetting multi-platforms on Docker (and the Linux/Unix world has always been CPU-agnostic, anyway).
No one is asking you to change your workflow overnight. It is absolutely true that if Apple pushes an ARM transition through too quickly - e.g. by letting the Intel models rot on the vine for two years before launching ARM machines - so people like you are stuffed as soon as you need to replace your current Mac - it will be a disaster. Yeah, being cynical that's pretty much what Apple have a track record of doing with the Mac Pro trashcan and the 2016 MBP. However, lets start with the glass half full and assume that you'll have 3-5 years for your workflow to evolve, and that Apple will recognise the need to work with and encourage key developers to port their products to ARM.
Unless Apple are completely stupid, they're not just going to take a chip designed for a passively cooled, ultra-thin, ultra-low-power tablet and stuff it in a high-end "Pro" laptop or desktop.
Here's what an ARM server CPU looks like: https://www.theregister.co.uk/2018/09/18/ampere_shipping/
...except, because ARM is mix-and-match, Apple might instead decide on different features to optimise it as a workstation rather than a server.
Go google USB 4 - which includes TB3 compatibility - the standard was released this summer and actual hardware is expected in a year or two.
That said - I think the ARM can has been kicked down the road a bit with the release of the Xeon Mac Pro (which commits Apple to Intel for another 4 years or so unless they want to look really stupid) - and the way iPadOS has been developing as more of a laptop alternative (personally skeptical about that, but its still happening).
