I am testing the daily built image of the upcoming Ubuntu 16.04 LTS (as of Jan 2016). And I see latest version of almost anything I want to use.
The question I have is, are these latest versions guaranteed to stay (or improve to a higher version) when the LTS is released? Or is it possible for them to be downgraded.
Unless they are proven to cause serious regressions, packages are rarely downgraded in a development release. Once the final version is released, the package versions are frozen. Updated versions (called backports) may be created on a per-case basis, and on request.