Secure Access server R7x cannot be upgraded to E80 / E80.x.
There is a solution for upgrading the clients by using Online Upgrades (See p.44 in the Endpoint Security Management Server E80 Administration Guide). However, the server must be replaced.
Secure Access and the new E80 Endpoint Management are completely different servers. The architecture of the applications has been changed, as well as the database.
For this reason, the E80 server also cannot communicate with R7x clients, so any mixed environment should not be attempted.
While Media Encryption can be migrated (see sk60502), for Secure Access this is not the case.
Note: Before installing E80.20, run the pre-installation validation tool (see sk65039).