This is a question for current developers and contributors (cstux and others). You should be aware that newest Spark version has switched to ..username\Application Data\Spark folder for storing user's settings and history (at least on Windows).
So, is there any plans or possibility to make installer (or Spark on a first launch) to search in the old place and then import old profile? If not, then upon launching Spark 2.6.0 Final we should inform users (in a blog post and release notes) that they should find a way to copy profiles to a new place before they upgrade their users (AD scripts, etc.). I have already warned the users in 2.6.0 RC1 release notes and blog post.