Adobe are ending support for Flash at the end of 2020,
Flash won't 'disappear' it'll just no longer get functionality and security updates,
so you'll be able to carry on using Flash in it's final form version,
where you probably will encounter problems is with browsers and how they allow Flash and how they accomodate functionality of Flash,
for me, with the Flash game I play, my problems started when Chrome went beyond version 65 & Firefox went beyond version 63,
Chrome started rendering my game in software mode instead of hardware acceleration causing horrible lag and generating a warning about an unsupported video card problem,
Google Chrome is a fork of the Chromium Project, after Chrome went wrong all the other forks one by one followed suit, Opera, Vivaldi, Yandex, Facebook Gameroom (which is really a mini browser based on Chromium)
when Firefox updated to version 64 it started storing the Flash cookies in the Windows 10 user account/apps section, this screwed up some functionality in my game too,
my best solution so far has been to identify the build of Chromium the last good version of Google Chrome was built on and install that developer build of Chromium soley for playing browser based Flash games,
it doesn't have all the google product integrations and api's and best of all it has no built in updater so it stays exactly as you installed it,
you do need to go to Adobe and install the PPAPI version of the Flash plug-in even though Adobe confuses Chromium with Chrome and thinks it's pre packaged,
if you fancy trying it here's the download location,
it's Chromium version 65 Developer build for Windows 64-bit systems (basically any Windows 10)
https://commondatastorage.googleapis.com/chromium-browser-snapshots/index.html?prefix=Win_x64/530358/
you want to download the mini_installer.exe file that's 2nd from the bottom, when you open that file it triggers the install process,
once installed, open Chromium and use it to visit the Adobe Flashplayer download site and install the PPAPI version of the plug-in for your operating system,
https://get.adobe.com/flashplayer/
from here on you just treat it like regular Google Chrome, a word of caution, as this browser isn't fully up to date with the latest security patches you should only use it for playing Flash games on trusted sites,
for all your other browsing needs just use your regular preferred up to date browser,
you can have Chromium & Google Chrome both installed on the same pc and they don't seem to conflict with eachother.
I installed the extensions AdBlock Plus & Disconnect, also for Facebook I use the extension Fluff Buster Purity,
an often overlooked point is that the first time you want to use Flash on a site you have to click on the beginning of the address bar and use the site Flash options to set it to: 'Allow'
after that you only have to click on the jigsaw piece at the end of the address bar and allow the plug-in each time your game loads.
I hope this is of some help.