The 13Mini has the A15 chip.
That same chip is in the current iPhone 14 and 14+, the current iPad mini, the current Apple TV… most of the products its in aren’t even a full year old yet.
Also, even newer products like the iPad 10 are still on the A14.
The A16 is literally only available in one product line, the iPhone 14 Pro.
Everything else is A15 or below.
Even the current Mac chip with the M2 is based off of the A15 processor.
All this to say, you should absolutely not worry about the 13Mini, or any A15 product, losing iOS support anytime soon.
Remember, it’s just been within the last four months that Apple stopped giving updates to products with the A8 and A9 cpus.
I wouldn’t expect products with the A15 to even be considered for software support loss until at least 2026, probably even later than that.
Edit: I just checked the support list.
I totally forgot that the iPad fifth generation, released six years ago this March, with the going on eight years old A9 chip and the actually going on eight years old first generation iPad Pro still get OS16 support.
One of their low end products from six years ago that had a processor two years out of date when it was released is still getting updates today.
There should be Absolutely no concern about the barely a year old A15 chip and 13Mini.
It’s quite possible software support for that thing could see the 2030s.