(Quick note: save games will not transfer from your Early Access build to release, but within the 72-hour period prior to launch, they will).
Does it say what I think it says? That EA game will be somehow transferred to the full game? An unexpected bonus..
Nope ...
Full game starts 3 days earlier ... you will ne limited to whole Act 1 during that time ... but after those 3 days end, you will be able to continue *THAT* characters.
Since they will be done in 1.0, there is no compatibility issue.

Anything created before will not transfer.