As I understand it, the Magic Keyboard has a scissor mechanism (both Apple themselves and Wikipedia call it a scissor-switch keyboard) with some additional stabilization that makes it less wobbly to type on than cheap scissor keyboards. Typing on one, you can feel that it isn't like other low-profile scissor keyboards that sell for 1/3 as much, but nobody mentions what that stabilization might be...
Unfortunately, the Magic Keyboard is probably a close relative of the keyboard in the pre Touch Bar MBP - if anything, the additional stabilization might make it a bit thicker (it definitely feels better than a 2015 MBP). The last 0.1" that Apple managed to shave off the Touch Bar generation (which is 0.61" thick, while the Retina was 0.71" thick) probably came largely from the butterfly keyboard.
I agree with all the other MBP aficionados on here that I'd gladly give the 0.1" back for a really great keyboard, but all of us disagree with Jony Ive, and he makes the decisions. The other problem is that, while the 15" MBP can easily take the 0.1", the MacBook, which is less than 0.5" thick where the keyboard is and (unlike the MBP) actually depends on its thinness, cannot.
Apple could very easily use two keyboards in the portable line - heck, they could use three with no problem at all. If they didn't have the obsession with one keyboard, the 15" (or larger), could use a larger keyboard with a number pad or Touch Bar beside the keys. The 13"MacBook Pro could use the same keyboard without the "sidecar", and the MacBook and Air could use a super-thin butterfly design.
Razer uses a unique mechanical keyboard in the 4K model of the Blade Pro, which sells fewer than 5,000 units per year - Apple sells far more 15" MBPs (alone) than that in a week. There was one year (2016) when Razer sold less 17" laptops (just under 1000) than Apple sells 15" MBPs in a day! Nearly trillion-dollar Apple can certainly afford to use a unique keyboard in their flagship portable if tiny Razer can use one in a slow-selling halo model.
The one keyboard thing is an obsession on Apple's part, but it unfortunately goes back a long way. The first time I noticed it was in PowerBook days, way back in 2003! The 12" and 17" PowerBooks had just come out, and the 12" was exactly wide enough to accommodate the full-size keyboard that would feature on all three models, which came within 1/4" of both sides of the case. On the 17", the keyboard floated in the middle of acres of space - a numeric pad would have fit without being cramped at all, and the half height function keys were just silly. Ever since, Apple's keyboard philosophy has been the same - the biggest keyboard we can fit in our smallest Mac carries throughout the line.
Are they aware enough of the reception of the butterfly keyboard that they'll finally give up their one keyboard obsession? I'm pessimistic... What we get in the MBP will most likely be dictated by the MacBook, which means either another butterfly or a haptic keyboard of some sort. I don't think the haptic will be ready in time for this year's release, and they probably want to put it in the MacBook first, so my best guess is another generation of butterfly keyboards for the MBP.