It will likely be last, but yes. Lily will be a challenge to get Plesk working on since there are tons of projects running on Lily using weird custom stuff that is not compatible with it. Lily will likely lose some of its capability to run various things when it finally gets Plesk, though it will obviously be easier to use.
For now, Lily is still available for users if they ask, but it works the same as it did on cpanel for the moment. You need a separate account on a Linux box, and Lily has no control panel.