The saved games are wiped in part to keep some of the many bugs which will get fixed from carrying over to a new update and being erroneously re-reported.
Not just on release, whey will probably be wiped every major patch during EA
They will, however, try to keep the old branch as an option, so you can continue your existing character if you want, but a new game will have to be on the current patch. See 45:33 in the video:
https://www.twitch.tv/videos/763351879
