This is a shitty move by Disney, but I bet they figured they'd given Tarantino enough concessions to this point that they could do something like this and not cause a huge uproar.
I mean, Tarantino's already basically got carte blanche to make whatever he wants. He writes a script, the Weinsteins give him however much he needs to turn it into a movie, and he makes a movie. With Hateful Eight, he went even further - not only shooting in 65mm (which is awesome), but going with an obscure/ancient widescreen format that practically no theaters can show anymore. Even theaters that already had 70mm equipment had to get new lenses in order to project at the right aspect ratio. Then you add the whole "roadshow cut," complete with overture and intermission - it's a crazy production, and basically Tarantino going "They'll give me what I want, so this time I'll ask for everything."
Which I think (hope) will make for a great cinema experience. And I sympathize with Tarantino, because it is a shitty decision by Disney. But Hateful Eight represents studios giving Tarantino more than he's ever had before.