Hello,
Based on https://www.arubanetworks.com/support-services/end-of-life/
enf of support is announced until 31th of August 2022 but end of development is still TBD.
I would say, yes you can continue with this firmware until August 2022. But start to think about renewal. Address that to your management to have some budget.
have a look about the end of development, in case of major security breach, I don't know if Aruba will develop a patch after the EOD.