In terms of OS support, definitely 6-10 years. In terms of being high performance with pretty much every app, probably 4-6 years. But most tech enthusiasts will probably be itching for something new in 3-4 years.
4 years ago, the latest iPad Pro had the A10X with 4GB RAM. Many of those owners that frequent this forum have probably upgraded or plan to upgrade soon, even though the basic tasks are probably still very functional.
For many here, functional is nice, but it’s preferred to be “cutting edge”. What that will mean in 3-4 years is anyone’s guess. Some have already predicted that the M1 will be dwarfed by the next iterations (which could also just be on Macs). What that will do to help with iPad apps, probably very little.
Maybe with better heat management, these devices will really soar, which could be another reason iPadOS 15 isn’t the big jump forward many had envisioned. With a next gen cooling system in place, we could see even more leaps.
Hopefully these comments have been relevant to the topic you wanted us to discuss. lol
Life expectancy isn’t just related to RAM, it’s also based on the processor. I’m pretty sure the combo of M1 and 8GB RAM puts this iPad head and shoulders above even the 10th or 11th gen basic iPad in the future.