Haven't seen Mackie say that.
I'm happy with Sam being Cap. Bucky, while the original choice in the comics, doesn't seem to be the right guy in the MCU. He was not too long ago the worlds most wanted man for murder. He killed the Stark parents. He has a LOT of trauma to work through. If he became cap, other than being from the comics, it wouldn't have made as much sense. Sam, on the other hand, is a good hearted soldier, personally groomed by Steve. He's the right guy. He'll be a very different Captain America, which I think works in his favor.
I still wish the movie had been 5-10 min longer and given cap a more deserving send off. The idea was genius, but could have been expanded upon a bit. Ah well. Doesn't tarnish my enjoyment. Excited to see it again in 3 weeks. Hoping to get tickets to see in IMAX in the Chinese theater in LA. Go big or go home.