Fantasy is big right now. We've heard lots of news about Amazon's new Lord of the Rings TV project, Game of Thrones is wrapping up but will have spin-offs, Netflix is producing a Witcher TV show, Showtime are doing a Name of the Wind prequel show, Starz have American Gods and even Spike TV is still trying to make Shannara happen. There are signs that the fantasy bubble may be cresting - Sony's Wheel of Time project still hasn't found a home despite it being a slam dunk - but I think there's still room for a few different projects out there.
One author whose work has not hit the screens yet is Guy Gavriel Kay. It's easy to see why: Kay's novels tend to be too long to make for comfortable two-hour movies, but too short and too self-contained for long-running TV shows that can be exploited for years on end. His books are also based closely on real history with (relatively) little traditional magic, which used to make them a tough sell. However, it could be a point in its favour with some of the other upcoming projects having a lot more magic and the need for high budgets, whilst Kay's work could be adapted a bit more easily and could tap into the Game of Thrones fanbase looking for more work that emphasises politics and characters over flashy effects.
One interesting solution would be to do Kay's novels as a Fargo-style anthology series, where each season has its own storyline, characters and actors but take place in the same universe, with events earlier in the setting informing events set centuries later. It would be an unorthodox approach, but could be interesting.
I'd see this series unfolding as follows, with each season corresponding to a novel (or series) with the setting and time period that roughly influenced the book following:
Season 1: The Sarantine Mosaic, 6th Century Byzantium, Justinian's wars
Season 2: Under Heaven, 8th Century China, An Lushan Rebellion
Season 3: The Last Light of the Sun, 9th Century England, Alfred the Great
Season 4: The Lions of Al-Rassan, 11th Century Spain, El Cid
Season 5: River of Stars, 12 Century China, Jin-Song Wars
Season 6: Children of Earth and Sky, 15th Century Dubrovnik, after the fall of Constantinople
It might also be possible to incorporate A Song for Arbonne, which takes place in a different world but is heavily influenced by the Albigensian Crusade in 12th Century France, into this scheme.
Tigana, although influenced by Renaissance Italy, features a very different world background with much more overt magic. It would probably be better served by a separate movie adaptation. The Fionavar Tapestry trilogy and its stand-alone sequel, Ysabel, could form another, separate TV series.
To date, the only interest in Kay's work has been from director Edward Zwick (Glory, Legends of the Fall, The Last Samurai, Blood Diamond), who held the rights to The Lions of Al-Rassan for a while. Hopefully someone will pick up the rights to Kay's work and bring it to a wider audience. One of the finest living fantasists, his work deserves to be better-known.