According to the post on the official forums, we will have 2 versions for DCS instead of the current one: 2.5 and 2.5 Beta. This is pretty much what we see in a lot of software out there, where there's a final version and a more advanced one.
ED tells us to not delete anything prior to updating as the updater will use a lot of the files and, if necessary, do all the cleanup.
This update will be delivered in 2 stages, with the 2.5 beta being released first (for those that are using 1.5.8 openbeta and the final one a in a couple of weeks:
Gentlemen, here is some explanations how your current 1.5 (and/or 2.2) will be converted to 2.5, please take a look the attached diagram. Transition will be made in 2 stages:
1 stage: Beta-version. 1.5.8 Open Beta will be updated to 2.5.0 Open Beta. Updater will check 2.2.0 (Alpha) and add necessary modules to 2.5.0. Then Open Alpha 2.2.0 will be uninstalled (user will be prompted about 2.2.0 removing).
1.5.8 release remains as is on this stage.
Some time (maybe one-two weeks, we hope no more) for wide test of this procedure.
2 stage: Release version. 1.5.8 release updated to 2.5.0. User will be prompted before update about saving 1.5.8 Final version in the separate directory.
Modules from 2.2.0 Open Alpha (or 2.5.0 beta - see 1st stage) version will be used for 2.5.0 installation, after that old 2.2.0 will be uninstalled (user prompted).
Open Alpha 2.2.0: this branch is no longer supported. If user have only 2.2.0 Open Alpha, updater will suggest to download 2.5 installer - it will install 2.5 release and remove 2.2.0 Open Alpha.
Home folders (Saved Games\DCS) remains the same (Saved Games\DCS and Saved Games\DCS.openbeta). New Saved Games\DCS.release_1_5 will be created for 1.5 Final version and all content will be copied into it from Saved Games\DCS. We also strongly suggest to remove Saved Games\DCS\Config\options.lua and make graphic tuning from scratch using DCS GUI because of 1.5 and 2.5 renders are significantly different.
Activations. All activation keys are saved in Windows Registry and NO additional activation needed.
1.5.8 Final version installer will be available on DCS site.