I am planning on taking RHCSA exam sometime in march or april this year and I know that exam will be retire on may.
My question is: If I pass and I want to take the RHCE exam after may would I be able to take EX300K?
No, because the EX300 (RHEL 7) exam will sunset as well at the same time.
Its replacement is the the EX294 exam (RHEL 8). Be warned, however; the RHEL 8 RHCE exam is not like the RHEL 7 RHCE exam.
You can see for yourself here for 7:
and here for 8:
Will the existing EX200 (RHEL 7) qualify you to take the EX294 (RHEL 8)? I'm told it will.
Perhaps someone more knowledgable can reply with a for-sure yes or no.