Lifespan of 2011 iMac
Given you’ve already done the work once, you will be the best to know.

SSD - always a great investment, plus they are almost always fungible - you can put them in newer gear with little to no degradation on speed if they still have life.
RAM - low risk upgrade as well. Especially if you don’t need to max it. Add it only when your benchmarks prove you need it - it’s almost always cheaper to delay buying and only buy when your time to fix the software causing RAM to blow up is worth more to you than the cost of more RAM.

That being said - the $800 Mac Mini will run circles around your 2011 iMac performance-wise. Especially if your software stack can transition to 64 bit speed and run in Catalina. Some old software, when migrated to new Mac hardware simply can not run. New outclasses substantially in every other way including power efficiency, GPU, storage, CPU, memory, expansion.
So for me, the tie breaker is the display - if you love and need it, upgrade or sell to buy a newer but used 27” iMac for value. Also, I have a hunch, a lot of people will want to sell their perfectly good iMacs very soon. This includes Apple if you have cash for new and want to make a deal when the line eventually refreshes. Apple will put machines on the refurbished / clearance rack starting immediately when a new model releases and then again when they claw back all the unsold stock from distributors and retail stores globally. With this bump, I wouldn’t wait and I’d shop to price what you need before next Monday and then have your card ready to buy if you get a short-sale opportunity.
With a Mac this old - there will be a very compelling reason to choose to upgrade, decide trade up to slightly less old or “break the bank” for the latest CPU with a T2 chip. Investing in newer everything can be a great value even if you don’t go new at the $400 range.