Granted, the Whisperers’ potential Fear the Walking Dead inclusion was something previously teased by Robert Kirkman, which coincided with Nick wanting to become one with the walkers in Season 2.
Even though Morgan is heading to Fear the Walking Dead soon, which possibly necessitates a Whisperers-friendly time jump, it would be a strange decision to port such a noteworthy Walking Dead comic group over to the companion series.
Especially after Season 3 expertly delved into how humanity is indeed the true evil in this world.