Kinda old news (by that I mean last Thursday), but since the DLC pack isn't out yet, why not?
First, track names. For the Egg Cup: GCN Yoshi Circuit, Excitebike Arena, Dragon Driftway and Mute City. For the Triforce Cup: Wii Wario's Gold Mine, SNES Rainbow Road, Ice Ice Outpost and Hyrule Circuit. That's right, two of the three retro tracks were already featured as retro tracks in other games, and I can't say I'm too hot about the hardest track in the entire series being one of them. GCN Yoshi Circuit, on the other hand, is a much better pick - I've always wanted to race on it with an inward drifter, so now's my chance!
There are also a few tracks based on other Nintendo series, as was expected. Excitebike Arena and Mute City were natural picks, and Hyrule Circuit only makes sense considering the title of the DLC pack, which includes "The Legend of Zelda". However, I can't help but think having Link on the roster and a track based on Hyrule may turn out to be a little jarring. Much moreso than the Mercedes thing, at any rate. But oh well, I won't knock it until I've tried it. For all I know it's going to be a perfect fit. (After successful crossovers involving Pokémon and Nobunaga's Ambition, as well as Zelda and Dynasty Warriors, I'm going to avoid passing judgement beforehand.)
Cat Peach is confirmed to be a middleweight, to absolutely nobody's surprise. This means there are now enough middleweights for everyone in four-player local multiplayer, though I guess if you care enough about weight classes to pick your character based on that, you're not going to be picking a middleweight of all things. No word on Tanooki Mario and Link, though I fully expect the former to remain a cruiserweight, like his suitless counterpart.
Finally, the vehicles: three karts, the Blue Falcon, the B-Dasher and the Tanooki Kart, and one bike, the Master Cycle. We also know the visible stats for the Blue Falcon, and they confirm what I suspect most people wanted out of these DLCs: vehicles with new sets of stats. Indeed, the Blue Falcon is the only vehicle thus far that provides a boost to both ground speed and acceleration. Of course, it's also very light, with crappy traction and average handling to compensate. The Tanooki Kart has bad ground handling and good traction, but we don't know anything outside of that for the time being.