Hello Linux Geeksters. As you may know, Ubuntu 15.04 Vivid Vervet, scheduled for release on the 23rd of April, 2015, will be using Kernel 3.19.3 as default.
Unfortunately, Kernel 4.0 and Kernel 3.19.4 got released after Ubuntu Vivid had reached Kernel Freeze, so Canonical could not implement either of them on their latest system.
Ubuntu 15.04 will be the first Ubuntu system to use systemd as the default init service manager, the Locally integrated menus will be enabled by default, Unity 7 and Compiz will receive important updates and the main applications will be updated to their latest stable versions.
If you are using either Ubuntu 14.04 or Ubuntu 14.10 and want to upgrade to Ubuntu 15.04 (beta), you have to perform a regular system upgrade:
$ sudo apt-get update
$ sudo apt-get dist-upgrade
Install the update-manager-core if it is not already available, and run the upgrade:
$ sudo apt-get install update-manager-core
$ sudo do-release-upgrade -d
Without any argument, the d-release-upgrade command looks for the latest stable version of Ubuntu available, but -d tells the upgrader to include the unstable versions also.