Not so fast -- (ha! get it? "fast"?) as Dariusmdev points out, this would actually mean that you'd have to buy even more Riding Crops, probably even throwing up the price on the servers. Because instead of getting one mount trinket and using it for all your mounts, you'd have to get one enchant per mount that you have. Good news for Leatherworkers if the change goes through, not so good for people who like to use a lot of mounts.
Which may be why Blizzard may have decided against the change at all -- according to Eliah, this change isn't actually implemented on the PTRs yet. So mount enchants are only in the code for now, and not actually available in the game. But it does show that the folks at Blizzard are actively trying to come with ways to help us handle trinket management, and that's definitely appreciated.