Hi SamAdmin,
Here are my findings:
1) When I did a fresh install of SPE 12.1 RU5 (Beta) it has following requirements under Host Integrity.
2) I did an upgrade from SEP 12.1 RU4 SNAC to SEP 12.1 RU5 (Beta). Upgrade contains these requirements.
Option " Only do Host Integrity checking through the Gateway or DHCP Enforcers is still there Probably because Symantec will continue to provide Tech Support services and bug fixes during the Limited Support period from the End of Life date until November 5, 2017 for customers with active maintenance.
Symantec Network Access Control (SNAC) End of Life FAQ for Customers and Partners
http://www.symantec.com/docs/HOWTO95154
There was no notification pop up on client machines after SEPM & SEP client upgrade. I don't think users will get any alert after an upgrade.
SEP Client upgrade will required reboot.
However I would recommend to test the upgrade prior to roll out in your network.