Warlord rebirth will come out next weekend and will have a champion's quest to go with it, any new players or rebirthed warlords may enter this champion's quest.
The benefits of the Rebirthing your warlord will be,
A chance at joining the champion's quest.(this time only)
+10 max to all base stats and skills.
+0.05 to your spellpower
16 Warlord poles.(Type /data to see locations)
Difficulty reduction for 2 of your stats.(Str Agi for Warr/Temp, Will int for Hara/Sorc, Brav Str for Seyan/Necro)
You will keep your crafting skills and all exp you have put into them (and the profession rank).
You will start with arch skills that you chose before rebirthing at 1 base.
You will keep your arch-race and be unable to change your race.

Warlord rebirth is live, it is located in Prospect peak in one of the houses for now. Beware you will lose all equipped items and depot items upon using the portal.
EDIT: It has been moved to the end of the castle quest.