With the change in pre-releases with the upcoming Brothers' War set, i.e. allowing all Brothers' War products to be sold by WPN stores at the start of pre-release week, including singles, we will se most of the sales from Launch Day shifing to Pre-release day.
I also expect, given that WOTC is really pushing drafts on pre-release weekend, that WOTC will slowly phase out pre-release kits in favor of booster drafts. Pre-release kits are more expensive to assemble than booster drafts and I could see WOTC dropping them as a cost savings measure. After all booster drafts and sealed deck tournaments were commone at pre-release for years before the arrival of the pre-release kit.