Hello jvniejen, What I would do is to get a backup of you data then do the upgrade.  As you can upgrade the MD in a degraded state it is just recommended to have it in an optimal state so that you will limit the chance of something going wrong on the upgrade process.  Also you will want to stop all I/O on the MD as well when doing the upgrade to make sure that it completes without any issues.   Please let us know if you have any other questions.
So I've got an old MD3000i with .06 firmware on it that needs to be upgraded.  One drive failed and our on-hand spares for this out-of-warranty unit only work with the new generation firmware.  Thus it needs an upgrade.  The hotspare is in use and working properly but if memory serves, the firmware updates will complain that the unit isn't completely healthy. Is there a method to promote the in-use hotspare to a full on vg member safely?  do i un-hotspare it and manually treat it as a replacement drive somehow?  Or will cross-gen firmware updates go totally fine in this circumstance?
MD3000i need cross-generational firmware upgrade with failed drive, hotspare in 
use