I've seen it, and if I add 2+2 and make some guesses Drazhar will kill Jain Zar, but Jain Zar will be reborn through Ynnead and defeat Drazhar and locking his soul into a weapon.
A side effect could be Karandras Rising up to be a true phoenix lord since Arhra is now gone.
Cegorach of course having a good laugh at it.
Given how willing GW has been to take a flamer to CWE lore to make Ynnari work, I suspect JZ is going to fly under the Ynnari banner soon, as an FU to Khaine, rather than "killing" her.
You can't kill a Phoenix Lord in any normal sense. When the armour becomes inactive, it will suck in another Eldar soul to power it back up again, but it retains the original PL soul/personality/memories. I don't think they would mess with that process.
That said if they do go for that option, it would have really big implications to the whole PL end times prophecies, which CWE is to some extent founded on. Which would be like using a D-scythe to the lore instead of a flamer lol.
My guess is it is a reference to Arha being the fallen PL and continues to exists as Drazhar being confirmed rather than implied. There is room in the lore, that Arha could have actually been killed and Drazhar being another Eldar which took over the armour while it was in the exarch stage, with Drazhar soul becoming the dominant one.
You could than have a relationship form between JZ and Arha, which would then explain why she apparently hates Drazhar more than Karandras lol.