There's plenty of information about that in the "future of wowace" thread in this forum, but to make a long story short:
- There will be a basic version of the client that is free. It will have all of the regular client features. You will need to click each addon separately to update it, but as development (trunk) versions will no longer be available, updates will not be as frequent; authors will have to mark (tag) specific beta and release versions, which will be available through the client.
- There will also be a premium version of the client that costs money. I haven't seen any word on whether this will be a one-time fee, a monthly subscription, or some other payment model. The premium client will be exactly like the free client, except that it will update all of your addons with a single click.
Alright, thanks for summing that up for me.