Greetings Vissox,
Upgrading your current Pre-Order package to a higher tier has always been a feature, and will grant you all of the items included in the higher tier pack. Upgrading was not removed, only sales of new Pre-Order packs.
So yes, if you were to upgrade your Wayfarer package to a package that includes Alpha Two access, you would be invited to the Alpha Two testing.
At this time, we have no intention of removing the upgrade option for the foreseeable future. But we will provide ample notice before that option is removed.
I am closing this thread. Feel free to make a new post should you have any other questions.