Please read the article containing the release announcement for 18.10 for the detailed answer to your question. Simply put, we have decided to drop efforts to release an additional desktop environment, but are working on ways to add Ubuntu Studio to any official Ubuntu flavor. For instance, you would install Kubuntu and add Ubuntu Studio to that for all of the same benefits. This is work-in-progress.

There are no plans to upgrade gimp in 18.04 at this time. The version of gimp that is in 18.10 will remain the same for its life. When 19.04 is released, it will have the latest version of gimp at the time of its release, but will not be upgraded further. 19.10 will have the latest version of gimp at the time of its release and so on. Ubuntu is a fixed-release distribution model, and the only exceptions that happen are in Service Release Updates which happen only in the LTS versions (such as 16.04, 18.04) which release every two years.

As DiVinci Resolve is proprietary software, there is no way to do that.