After Sega and Sammy merged, Guilty Gear became an issue. Arc System Works developed the game, but Sammy Corporation owned the IP. During the shuffle, Guilty Gear transferred to the newly formed Sega Sammy Holdings.
Arc System Works went on to develop BlazBlue, but they haven’t forgotten about Guilty Gear. When we spoke with Daisuke Ishiwatari, creator of the series, he promised fans a new Guilty Gear would come "eventually."
When that day comes Arc System Works won’t have to worry about Sega. In Japan, Arc System Works recently filed a trademark for Guilty Gear, which was published on the Japanese trademark database today. If Sega retained the rights to the series Arc System Works wouldn’t be allowed to trademark the title for video games and related categories. It seems Arc System Works reclaimed the rights to the Guilty Gear series by purchasing them from Sega. We’ll check in with Arc System Works to see if they have anymore information regarding this trademark and the future of Guilty Gear.
Update: Arc System Works responded and confirmed that they completely own the rights to Guilty Gear now.