I think the most important question is: Will Blaze 2 be 100% (or close to that) compatible with Blaze 1? I myself am that kind of developer who isn't doing "development for development's sake". I primarily care about my project and I want to keep that up & running and develop it further. That's also the main reason why I am still on Meteor 1.2. It works, and I get everything done with it. No need to experiment with npm packages, React and all that other cool stuff. Don't get me wrong: I love innovations, but my priorities are focused on the progress of my project.
If a Blaze 2 would mean: still Blaze, but much better, I wouldn't care if it uses Vue under the hood or the old Blaze technology. But once I would have to adjust all my template code to migrate, I would rather go for React. Mainly, because in this case I would completely loose my trust in a technology that only exists in a small niche, like Meteor is. Why should I invest again, just to switch to another niche approach that eventually may or may not be successful?
Having said this: I really appreciate the drive coming up in the Meteor community around Blaze, thanks a lot for this! And you "hard-core devs" most likely know much better than me what makes sense from a technical point of view. But please don't forget all those people who have already invested in Blaze and want to rely on compatibility. It totally makes sense to break compatibility if technology moves on. But just to get a bit more performance out of it wouldn't convince me.
BTW: Has anybody already asked Evan You what he thinks about the combination? He used to be an active Meteor dev and was an MDG statt member, so he should know it very well.