I'm not aware of rumors of an update any time soon. As it shares the same M1 CPU as current M1 Macs. It likely won't get updated until they get updated. Which isn't rumored until 2022.
The Macs currently rumored for updates are the higher performance Intel models. Which will likely get a higher spec version of the M1 informally dubbed the M1X. Said CPU is likely to have a higher power consumption than the M1. Which would not work in an iPad.