As announced over on the official Guild Wars 2 site boosters have been overhauled.
There will now only be three main types of boosters, each lasting 2 hours:
- Experience (essentially combining kill streaks, PvP reward tracks, and +50 game mode)
- Item ( essentially combining crafting, gathering, and magic find)
- Heroic (applies both #1 and #2 above)
As for the rest, per the announcement:
Celebration, strength, armor, rejuvenation and speed boosters will continue to drop randomly from Black Lion Chests, and birthday boosters will be granted on character anniversaries