GNU Emacs 19 will support a broad spectrum of machines, like Emacs
18. Ensuring this is the purpose of the testing we are about to do.
(Please don't volunteer; we have enough pretesters, and if more people
offer, dealing with those messages will slow things down.)
Once we make sure it is indeed working reliably on various different
systems, we will have a public beta test release.
Emacs 19 does support adding properties to ranges of text, and using
these to switch fonts. In the future, the Epoch people will help
merge support for variable-width fonts.
Meanwhile, I have almost finished updating the Emacs Lisp manual. Its
next edition will describe Emacs 19. There will be an announcement
when we know when this edition will be available.