I don't know -- it doesn't particularly excite me. All I care about is HTML; I don't need semantic markup beyond that. All most users care about is what they can see; what it means is implied, and only important in so far as the meaning is clear to the reader. Writers write for readers, not for computers.
That said, I am very interested in microformat support, which is kind of schema-related (but very loose schemas mixed in with content). I don't think anything has that now; part of why the community and code matters to us is because we want to build on this, we don't just want to use the product. A more semantic/abstract editor has some advantages here; but I'm not sure it's enough of an advantage, especially compared to a more mature product (and maturity really matters for this case, as there's tons of little usability issues).
One of the plugins I like for Xinha is the stylist plugin (to see it you have to look at the demo and select Stylist). I think there's some hidden potential in that, or something based on it.