I seem to recall that there was a small amount of "outrage" when the Destiny Knot mechanics were revealed - you no longer had to learn the noble art of RNG manipulation to get semi-perfect IVs! Now any casual players could invest a few hours and a few dozen slots of Box space and get a perfectly-IV'd Pokémon! The change from RNG manipulation to Destiny Knot breeding changed IV-tuning from a hopeless/broken mechanic into a merely tedious one. And now they're removing the tedium too. This makes the art of IV manipulation so much more accessible, greatly reducing the entry treshold for things like VGC or the Battle Whatever. While also keeping most Pokémon unique, for all practical purposes.
I won't be missing having box upon box full of breeding rejects, intermediate-step-parents and other worthless 'mons staring at me with their big, beady eyes every time I browse my ingame PC. Well-meaning, cute creatures destined to be released, given away for scrap at the Wonder Trade, or remain in my PC boxes forever. A system which produces so many excess Pokémon, no better than junk, isn't quite in the spirit of the franchise. The amount of iterations you need to go through is greatly reduced with the new system, the dice won't have to be thrown as many times, and even almost-perfect breeding rejects can be acceptable. Right nature, right moves, right gender, lacks a few points in HP? No problem, fella, you're good enough. And no longer will you have to soft-reset hundreds of times to get decent legendaries. A half-dozen times to get the right nature, for old times' sake, but even without the endless chore of flying to the IV checker every time.
And as
Vader_the_White said, getting a 6 IV Ditto will be trivial now. Getting 6 IV Ditto of every desirable Nature will be easy too. Those who like breeding just had their treshold lowered too.
Now for some speculation: It's specifically mentioned that the Japanese event Magearna will be holding a
Silver Bottle Cap. It seems like there will be more types of Bottle Caps, then. If I may guess (this is teetering on the edge of what is allowed, but I find this plausible enough to try anyway):
Silver Bottle Cap = Raises the IV of one stat to 31. Moderately rare/expensive.
Gold Bottle Cap = Raises the IV of all stats to 31. Very rare/expensive.
Normal Bottle Cap = Raises the IV of one stat by 1, 5 or possibly even 10. Fairly common and easy to find/buy.
If I were to implement this system, I'd also have a "Black Bottle Cap" or a "Rusty Bottle Cap" or something to
decrease IVs too, but you never know with Game Freak. It's also far from certain that the Silver Bottle Cap will be the second best one, in the Zelda series there are Silver Rupees but not Gold ones, for instance. Either way, I'm perceiving something like a Vitamins/Wings system, with several kinds of IV raising items, some cheap and ineffective, others expensive and effective. Hopefully, the former can be applied in bulk, unlike Wings which have to be applied one by one.
It may also be that the Bottle Caps, like Vitamins, are sorted by which stat they boost, in which Silver could be used for... Sp.Def, I guess? Either that, or any of the five others.
Disregarding Hyper Training for a moment, I think the Japanese trailer shows how Mimikyu's appearance changes after its Ability is activated: rather morbidly, the "neck" snaps and the head falls over to the side. We won't be seeing "True Mimikyu", then, but luckily the system allows for a great number of different costumes.