TeX is evolving with LuaTeX appearing to get some momentum. Given that almost no one uses TeX directly, I'd expect the biggest change would involve a gradual "

TeX is evolving with LuaTeX appearing to get some momentum. Given that almost no one uses TeX directly, I'd expect the biggest change would involve a gradual "improvement" in the macro library. It may even result in an embedded TeX à la sweave. Wolfram is hammering against the interactive element with CDF and I could see TeX being extended to support a more dynamic electronic document format if HTML rendering engines continue to be typographic messes. Perhaps an LLVM-type backend to generate executable ebooks would be an interesting project, but I'm not sure I'd start with TeX except for math markup. I would hope my prediction of the death of TikZ and PGF would come true soon enough, though.