Beta client will be used as final release client with an update or we must download all again?

Hopefully it'll be a fresh re-download unless there's an open beta or we get to download in advance.

Giving beta testers an advantage, even if a few minutes or hours, is just going to cause an uproar for no reason.

I think having to re-download it just to circumvent an uproar is a complete waste of resources if it can just be updated.

Much better than servers getting overloaded from too many people trying to re-download the client (not saying they will, but still think it's a waste). It's also common for people to pay for their traffic/bandwidth usage now, so that's 20+GB down the drain for them.

Probably depend on how ready they are on the open beta. If they are pretty ready they probably use the release candidate for open beta and might be able to patch it.

This is probably true if the open beta is a week before release, if the open beta start in an month I guess you have to re download.

Normally you will have to download it again, but thats a good thing, because there were alot of changes in Beta and im sure there allready lots and lots of stuff you woudent need on your harddrive.