As per the release announcement, a new install of LL 2.8 will carry Linux kernel version 3.19. If you already have LL 2.6, your kernel will not be updated to that. Newer kernels adopt drivers for newer hardware and dump drivers for older hardware. So upgrading for upgrading's sake could possibly cause some things not to work. That's why the development team opted not to include the kernel upgrade in the upgrade package.
It is easy to upgrade from version 2.6 to 2.8. You just need to run the Install Updates utility and then run Lite Upgrade. Follow the instructions and reboot afterwards. As an extra layer of precaution, I created a Systemback restore point before and after running Lite Upgrade.