amazon.jp knows all. They're still advertising a three volume compilation of Channel Five with a stand-alone story that will complete this 'uncompleted saga.' Volume three has yet to appear, after four years, and I'm sure never will. Given how many unfinished sagas I have of my own, I'm in no position to complain; but Shibata does do this. Well, and so do many mangaka: the system seems designed to wear them out and throw them away.
So I'm (re)reading her ancient Shounen Jump series Freeman Hero instead, with a view to emptying some of my manga shelves. S-i-l says 'in ten years I'll be 78, and if I haven't read all those books by then, out they go.' This is probably a good policy to follow.