Pretty cool read, I really don't think its a issue if they lost the rattle. You can't hear other venomous snakes warning you (besides maybe a hiss). Don't forget rattle snakes have body language when they're going to strike just like any other snake. The rattle is just a sound warning so I really don't see this effecting anything but definitely really neat how some are getting quieter.
I mean we have rattlesnakes here in PA in our mountains which is 45 min away. But for example I live in the country and I have never seen one in any of my woods in 26 years of playing in them growing up.They just stay up in the mountains and survive our cold winters in large snake pits. These snakes are very interesting indeed of how they have evolved and live in general.