The more I think about this, the more convinced I am that Canon will tend to stick pretty close to their normal naming conventions. History seems to support that.
The 5 series has always catered more to wedding, landscape, studio photographers. It also represents the first full frame from Canon. It also represents the higher resolution bodies.
The 1 series, after the introduction of the 5D, leaned more toward action, sports, high frame rates, etc.
The 7 series so far has always been a crop sensor, but high capability type body.
The 6 series, has been full frame, and a budget conscious version of a 5 series.
Even the 3 series, has consistency. It was the first with eye controlled focus in the 90s, and it is the first digital with eye controlled focus as well.
So far everything Canon has done has stayed inside this naming convention (at least since the introduction of the 5D). If there are exceptions I'm not aware of them. We are going on two decades of this naming convention, I don't think they are going to arbitrarily mix it up now.
Considering that, it would be stepping well outside the conventions to have a 100mp 1 series. It fits the 5 series. This isn't a question of will or can they make one, I'm quite sure they can and will. I'm very curious about the name however.