Based on discussions in-game and this thread, I think this is the most likely conclusion
- Stats/Parkourlog separated into "All-Time" and "Seasonal"
(Alltime wont ever reset, seasonal will)
- Rankups, prestiges will need to reset because these have been revamped
- Mana and ender pearls will reset, and crates etc. will be rebalanced
- Nothing else will reset, you'll keep your inventories, vaults, echests, perks, titles etc