Wasn't Swarmlord always an HQ though? We can't extrapolate what may happen to Grimnar from what happened with Swarmy. There is still a very good chance the Grimnar become an HQ again, especially with guys like Reece and Frankie as part of the process.
I can see chariot-Grimnar getting stats between what he is now and a primarch this edition. I expect T7-8 and 9-10 wounds on chariot. Although I do not expect him to be as killy as Roboute. Maybe still a character to be able to get look out sir and run with TWC.
Edited by Wolf Guard Dan, 22 May 2017 - 11:37 PM.