06-25-2012 02:04 PM
It will update to version 8 as soon as Sophos is confident that the majority of older systems running 7.3.x will have no issues with 8.x.
If you're running 10.7 and have had no problems with 7.3.x, you can choose to re-download the installer and use it to upgrade to 8.x, likely with no issues. if you DO have issues, keep your 7.3.x installer handy so you can uninstall 8.x and revert.
Most people running 10.5 through 10.7 are not having issues with 8.0.x -- with the next point update, 8.0.x will also be ready for 10.8.