No way to predict the future. I ran Quicken Mac 2007 for years after it was discontinued. If you don't update your macOS it will probably run longer. If you do update macOS you can do what I did with Quicken when it wouldn't run and run the older macOS in a Virtual Machine just to run that application. I used VMWare Fusion at the time but it was annoying as it didn't have graphics acceleration (the screen refresh was slow). But Parallels today has that and it works very well. 

I eventually bit the bullet and upgraded to the new version of Quicken, which is subscription (and not even an Intuit product any longer).  It works but I still liked the older one better.  And my financials got messed up switching (despite the converter working...  I'm not sure why).