The promised rewards could be anything from crafting items to Crown Crates, although it’s not yet clear whether the rewards will be randomized or based on frequency of logging in. There will also be new daily rewards for the first Battleground you complete per day, giving you a bit more reason to log in and do something on the regular. It’s easy to miss it amidst the expansion feature list, but it’s a pretty important change just the same.
Source: Official Site via Reddit