Hi, @Ali Mostafa Welcome to Microsoft Q&A, Thanks for posting your question.
Yes, we will stop V4 support at some point, but we do not have any planned date currently
we will give plenty of time and notice to customers before retiring redis 4.
you can upgrade your existing caches from V4 to V6 currently from the portal. Usually, there is no client application change required to upgrade to V6.
Regards
Geetha