A flurry of super telephoto patent applications appear

Japan Patent Application 2017-215495

This patent appears to be two fold, lightweight (relatively here!) with a good correction of aberrations such as axis chromatic and chromatic aberrations of due to magnification.  This element design most likely has IS, it's simply not labelled by Canon.

• 400mm 2.8
• 300mm 2.8
• 500mm 4.0

Japan Patent Application 2017-215494

Reduction of chromatic abberrations and secondary spectra (specific type of chromatic aberrations) are reduced in this patent. This element design most likely has IS, it's simply not labelled by Canon.

• 400mm 2.8
• 500mm 4.0
• 600mm 4.0
• 800mm 5.6

Japan Patent Application 2017-215493

DIfferent technique to reduce aberrations such as axis chromatic and chromatic aberrations of due to magnification.  This element design most likely has IS, it's simply not labelled by Canon.

• 300mm 2.8
• 400mm 2.8
• 500mm 4.0
• 600mm 4.0
• 800mm 5.6

Japan Patent Application 2017-215492

DIfferent technique to reduce aberrations such as axis chromatic and chromatic aberrations of due to magnification.  This element design most likely has IS, it's simply not labelled by Canon.

• 300mm 2.8
• 400mm 2.8
• 500mm 4.0
• 600mm 4.0
• 800mm 5.6

Japan Patent Application 2017-215491

This application changes the element location for focus to reduce weight, and also to reduct chromatic aberrations.  This element design does not have IS, which probably makes it exploritory or defensive in nature.

• 400mm 2.8
• 800mm 5.6
• 200mm 2.0

All of these patent applications do not explicited mention IS.

However in most of canon's lens designs, this element grouping is the IS group.

On these respective patents, you can clearly see that element group in most of these lens group diagrams on the individual patent applications, it's simply not labelled as IS.