From the dev stream 17-11-2017.
This is my braindump
December update:
1. New: Crosshairs (40), diffrent colors.
2. 2vs2 TDM will be more supported. (tourneys?)
3. New fast duel map, lockbox style with doors (sound queue).
4. Some champs built up speed while walking (Scale, Galena, Clutch) for new players. Strafe jumping will get you there faster.
5. Ranked Play for Duel (diffrent classes highest Elite)
6. New Champ (not revealed yet)
7. Max FPS / Cap FPS (good to influence upload bandwith) sync with monitor refresh rate.
8. Datacenter(s) and starting gun saved.
9. Nerf for Anarki: -max speed. (Short boost in speed while injecting) < To hard to hit.
10. Nerf for Slash: -max speed. < To hard to hit.
11. Nerf Doom slayer, -beserk hit distance. < OP
12. Buff BJ hitrate (ability) will be increased a little.
13. Tribolt will be changed to sticking projectiles until being walked over or explode later. (area denial).
14. New Spawn 3rd person image (same spawn time cannot be hit) You can see your own custom champion.
15. Small armor respawn time (change) from 15 to 30 seconds.
16. Fix FPS to hitrate.
17. Winter stuff (season events).
18. Buff in Health for all Champs (reason is longer time to live).
19. Buff in Armor for all Champs (armor control will be more important).
20. Mod Instagib will be added
21. CTF will come in 2018
22. Hitboxes will be changed Januari/Februari will not be as a blanket over the model. But a better more adjustable solution.
23. There will be changes to Lore. (not in December?)
24. There will be changes to runes (easier / better reward) (not in December?)
25. There will be changes to loot boxes (more rare items) (not I December?)
26. LG change where if feels better than it is now, more like the old way but without the exploit.
27. Gauntlet hitrate extended. (can't hit as fast)
In general: They feel they are on the right way with the Quake and also the netcode, there will be performance 'improvements' in the December update.