I PERSONALLY don't think grendel has legs. I think with the 22 and 6mm ARC coming out we'll see those take favour over the Grendel. That's not to say the grendel won't be here in 10 years or so, just that the newer carts in that class are probably going to be more popular given their direct support from Hornady and their superior ballistics.
Grendel is a great cartridge that paved the way for where we are now, but it's been a bit superseded.
To give grendel it's dues though, i think it's better for pigs than 300blk or the other smaller class carts and in an AR platform it's still a really good option for it's class.