We know that Wicked City has already been licensed by Seven Seas...
Seven Seas only licensed the original 3 volumes of WICKED CITY. They did never license any of the numerous sequels that exist in Japan. In fact I asked them about it any got this answer:
Our license was for the three novels that make up the core Wicked City trilogy (The Black Guard, The Other Side, The Scarlet Clan). As far as I've heard, there are no currents plans for Tor/Seven Seas to release any of the later spin-off or side-story novels that are set in the Wicked City universe.
So that leaves the following WICKED CITY books untranslated:
凶戦鬼（妖獣都市異伝）Wicked War Demon (Wicked City Spin-Off) / 1 volume
妖獣都市《ニューヨーク魔界戦》 Wicked City: New York Demon Realm War / 2 volumes
妖獣都市 魔獣児 Wicked City: Demon Beast Child / 1 volume
妖獣都市 雪洞鬼 Wicked City: Snow Demon / 1 volume
妖獣都市 魔王眼 Wicked City: Demon King's Eye / 1 volume
妖獣都市 海死記 Wicked City: Sea Death Chronicle / 1 volume
妖獣都市 黒天使 Wicked City: Black Angel / 1 volume
I don't speak or read Japanese very well so those English titles are just educated guesses made with the help of an online automatic translation website. There are most likely mistakes.
These are actually the only Kikuchi books that I still have on my list as must-reads. I'm sure he has written a ton of other excellent books but - like many, I'm sure - I was introduced to his worlds via the anime adaptations and as such am just dying to find out what other adventures Taki and Makie have had.
I don't know what the legalities of picking up a series that another publisher started would be but I'd be happy if you could at least consider it.
And if possible, please pass along my compliments to Eugene Woodbury. I really enjoy his translations and so often the immense work and care that a good translator has to invest to come up with a result that is not only faithful to the original text but also flows well in its new language gets overlooked.