I think it's jumping the gun to assume that the ongoing series isn't going to happen. My guess is that Sebastien is waiting to see how the Legion hardcover sells to determine the fate of the ongoing. Here's what I think needs to be done to keep the ongoing alive:
1. Like the hardcover, print only as many copies as are ordered. At least at the beginning, to keep costs down.
2. Get the book out on time. Preferably monthly. But regardless of the schedule, the delays absolutely have to stop. Otherwise, the only people left buying the title will be the most die-hard of the die-hards.
3. Concentrate on getting Ghostbusters up and running smoothly before attempting any other projects. Keep Tron on the back burner for a while, so GB can get a foothold and a following outside the core audience.