I noticed that I'm a few (several) software rev's behind. I think it might be asking for trouble if I were to upgrade the C25's just for the sake of being current before migrating to the new C35's. With all the changes going on my inclination is to migrate at the current version after the NetSight upgrades, and let things run smoothly for a bit. There's no pressing need that I'm aware of at this point where the 10.11.03.004 wouldn't be sufficient. Our new AP's are supported by that software. (Unless the migrating configurations documents recommend it of course.)
We're an educational institution, so I need to be done by the end of August. Our next "break" is december so I'm thinking hold off on the C35 software upgrades till then if needed.
If you have access to the software manuals you should look at the section..."Migrating the Platform Configurations" in the ExtremeWireless Maintenance Guide. There are sequential steps for migrating a configuration.