GATE 7's appearance in the magazine is listed to take place in the future, you can see it listed in the magazine's upcoming line-up here and here.
This could mean that the relationship between CLAMP and Shueisha hasn't been compromised and the reason why GATE 7 is currently on hiatus may lay on different, yet unknown issues.
More information as they come!
Thanks revolution_d1 for letting me know about this! ;)