If there is an R mount aps-c camera, it might be a little grandiose to call it a line. I think it would likely be a niche camera mostly to get some more reach on long lenses without spending more for longer lenses and bigger camera sensors and processors.I generally tend to agree.
* EF mount full-frame mirrored line (in at least two segments (1D and 5D, plus the desired 7DIII)
* EF mount APS-C mirrored line (in two segments, 90D and Rebel series)
* R mount full-frame mirrorless line
* R mount APS-C mirrorless line
* EF-M mount APS-C mirrorless line
Well, seems like a lot of lines. I'm all for the more options the better, but at some point, there has to be too much. If they added R-mount APS-C, something else would have to get consolidated.