It won't stop working. Flashplayer has already been discontinued for web-browsers but the game is a .exe so it's all good. Newgrounds is also making the newgrounds player which allows you to watch / play flash games on their site. It's a little bit of a hassle to get working ATM but it does work.
Here's the NG player.
https://www.newgrounds.com/flash/player
and Here's the thread to get it working