Updates
I just bought the iPad 2021 (9th Generation)
Since it is still using an A-series processor unlike the others that are using M-chips,
I am just worried about how long will it be supported with OS Updates.
4 years? 3? 5?
iPad (9th generation)
While Apple does not pre-announce end-of-support for any of its devices, to date the majority of iPad models have received system software updates for five to seven years from their initial release. Update support will continue until such time as individual devices have insufficient resources (usually RAM) or CPU capability to support a system software update, or provide adequate performance.
As such, it is perhaps reasonable to assume that your 2021 iPad9 will have many more years of full support before you may need to consider replacement.