I'm going to buy a new expansion. Will I have to pay more if I buy the main pre-order now, and later, closer to the release, I'll buy the "annual expansion"? Will it be discounted with a pre-order, or can it be purchased separately?
It will be cheaper with the bundle. The campaign is $50 and includes one season. Each additional season is $10 and the dungeon key is either $20 or $25. You aren't saving more than $10, mind you, but you also don't get charged until right before launch.