Originally Posted by Morkai Almandragon
Is it already confirmed in the release? Or just a rumor? Also would that block root? or just recovery and roms?
It isn't a rumor - SELinux has been present in Android since 4.2, but operating in "permissive" mode (which basically blocks no violations, but logs the violations which occur). This was done to give an opportunity to app/framework developers to modify their apps so that they will not fault once SELinux changes over to enforcing in KitKat (4.4). This has been in the Google road map for a long time.
Of course, it can be turned back to permissive mode in a full custom ROM, so my comment applies to stock or near-stock situations. In particular, the initial rooting operations may get more technically difficult to acheive.
(With SELinux enforcing mode, a root user identity obtained by an exploit can have very limited capabilities, depending on the process context of the attack vector)
For instance if you were to accept an OTA on lightly-rooted stock, and then lose root during an OTA upgrade, it might be quite difficult to re-attain root.
Recovery and ROMs are already quite limited (for retail VZW N3 devices) because of the trusted boot enforcement.