I'm all for a Mac tablet, but not because I want a hybrid device--I just want a (somewhat mobile) Mac with pen input for pro digital art. I don't care about touch or iOS apps, although it would need to support touch for logistical reasons. But that's where the problem comes in. Neither OSX nor its applications are designed for touch (and won't be any time soon), therefore it would make for a less than optimal user experience. And we all know Apple is not prone to release anything that it doesn't believe is a great user experience. And I honestly don't think Apple cares enough about my niche demographic to try to create such a device anyway, even with the existence of the SP3. I think most people want a hybrid device so that they can have a productive and casual device rolled into one. But Apple has been very clear about what it believes regarding hybrids.
That said I am still looking forward to the iPad Pro announcement. Though it won't replace my Mac (+ Cintiq), it could make a great ancillary device, on a couple conditions--decent apps and (free) seamless file transferring support between the iPad Pro and my Mac, and of course pressure sensitive pen input. I think that's as best as someone like me can hope for realistically.
people often claim that what apple spokesmen said at one point is how they'll continue to operate forever. just look at all the things jobs said that he 'against all indications' oversaw in secrecy. misdirection is a key component to successful competition. and i know i mentioned adobe software specifically and you say it's a niche category (which i disagree with honestly), but a computer/tablet is in no way catered to only 1-2 types of people. if it can run adobe, it can run other software that millions of other pros use on their desktop. it would be great for MANY 'niche' categories, which isn't 'niche' at all. it's huge.