We all have our own opinions. I think Valkyire was a flash in the pan. I remember Shot Show 2019, every booth had something Valkyire. This year, everyone had a .300 BLK.
The .300 BLK is proving to have a place as a Close-Quarter Rifle / Pistol. Great for home defense and a superior truck gun.
The 6mm ARC is making in-rounds with the military, so I think that one will stick, but lightly.
The 5.56mm rifle is not going anywhere, and it has a long history of use and evolution. I would start with a solid 5.56mm rifle in 16" to 20", and then talk about what is next. Individually, and as a business I did not make any transition to .224 Valk. I do have one 6.5 Grendel, but we have not sold that rifle. I am still wondering why I have the Grendel. Mark LaRue convinced me it was a better round. I think he is correct, but the 6.5 Grendel cannot swim upstream against the 5.56mm in terms of market appeal. It will be relagated to an interested rifle.
I am sure someone will argue (I am not arguing back) that the .224 Valk is far superior to the 5.56mm NATO. It might be. I am old enough to remember the Betamax v. VCR arguement. One was better, one had market presence. We still have some VCR tapes around, but I have nothing Betamax.