For people who have never been in a beta before, it is standard practice that characters are completely wiped at the end, with absolutely no carry-over whatsoever. Beta tests usually take place on a separate server (or servers) that will not be live when the game is released and are usually retained for testing purposes after the game is released for expansions and other features. There are a lot of reasons for this, one is that you've been playing with a character that may have bugs, and has been playing in an earlier version of the game than what will actually be released, which may cause problems with the software. Another reason is that if they allowed characters to carry over, it would give those people a vast head start over anyone else in the game, which isn't fair. Yet another reason is that this is a beta test. You're there to test the game, find bugs, and squash them. You're not there to play the game as you would at release.
Some companies have allowed a very brief head start period for early subscribers/pre-orders (Warhammer, Aion, STO). Some also allow you to reserve your name, create your character, and choose your server beforehand. Squenix may allow this or not, but it's really way too soon to tell or even speculate. Regardless, don't expect to carry over anything from beta.