Bguy7
The Dragon Lord
Well, for all we know, it could be more so an alternative than a replacement. This way you can still use HMs on your own Pokémon, but not be stuck into needing to have a Pokémon with Cut in your party when you really don't want to. They could even reward you by using HMs, like only being able to get items from Rock Smash if you use your own Pokémon.
I suppose that would be better than getting rid of them all together, but it would still massively devalue the HMs. Though, I suppose they've been devaluing them for the past two generations anyways.