If someone can find the authors of the old setting books, and they are amenable, it may be possible to work out a reprint deal via TGC, though as Tim notes all the Fantasy Hero stuff in the old books would have to come out.
Alternately, we'll certainly entertain new articles on either historical rules and/or historical settings in the Guild Companion magazine. (We've published a lot of Mythic Greece -related articles and some Robin Hood ones.) If someone feels really brave, they are welcome to contact me about writing a new historical sourcebook.
Best wishes,
Nicholas