MK8 first, since I said some false things last time. Namely, Cat Peach isn't totally identical to other middleweights: she trades off some weight in exchange for a bit of extra acceleration. Same for Tanooki Mario vs. the cruiserweights. Whether this is useful or not depends on whether you'd hit an acceleration tier with the extra boost, otherwise you're better off using the regular characters. Link, on the other hand, is just a plain ol' heavyweight, no strings attached.
I already mentioned the stats of the Blue Falcon in my last post on the subject, but now we also know the visible stats for the other vehicles as well. The Tanooki Kart has average speed, slight boosts to weight and traction and slight drops to acceleration and handling. The boost to traction is pretty big in reality though, because most vehicles feature a decrease, which can sometimes get massive. Too bad traction's uses are pretty niche. The B-Dasher is a straight-up clone of the Mach 8, unless the hidden stats turn out to be different. Finally, the Master Cycle features inward drifting, no change in acceleration or weight, a slight speed boost, a solid handling boost and a sharp traction drop (though not as enormous as the other inward drifters).
Now, on to ORAS. Something called "Episode Delta" has been revealed in CoroCoro. As the title implies, Rayquaza will be playing a major role in it. Maybe it's an attempt to incorporate a story around catching Rayquaza? Either way, Deoxys is also said to be involved, though whether it's obtainable is another story. My money's on no, but if it is, will the whole thing be distributed like an event, or will it just be there (as the spiritual successor to the Looker Bureau arc, as many are speculating)? More on this, well, in about a week or so.
In addition, more legendaries from gens 2, 4 and 5 were shown to be obtainable, with only Giratina and Kyurem now unaccounted for. Considering they said every legendary would be obtainable between X/Y and ORAS, I wouldn't worry about them not being there, but if they really aren't, that's an odd choice to be making. "Let's make ALL legendaries available... except these two." Sure.