Where is the official new Ubuntu release feature list?

Solution 1:

• There is no official features list as of yet for 15.04.
• Debian plan to integrate systemd as default in their 8.0 release (codenamed ‘jessie’) and this release has not got a release date yet.
• Since work on 15.04 already started I would expect systemd not to be included in 15.04 (for 15.04 to have systemd I would expect 'jessie' to be ready).
• For that matter I would expect 15.10 to still have upstart with an extra installer to replace it with systemd where 16.04 would have systemd as default.

Solution 2:

For each new release there is a cycle of definition then freeze of features that will or will not be included. Anything discussed before that date is premature and may change.

Usually Feature Definition Freeze will be some weeks after uploading the toolchain followed by a definite Feature Freeze approx. 2 months before the final release.

The schedule for the next version is not yet published but you may have a look at the schedule from the last release (Utopic Unicorn release schedule) to get an idea.

This is why at present there will be not yet be any "official" feature list.