Yes, quad-pixel AF was one of the few things people were thinking would be a significant improvement over the R3/R5 duo.
So what's left?
- Increased resolution versus the R3 would certainly be nice for me (it's reason I don't shoot the R3), but Canon had long tradition of disappointing on resolution increases with the 1 series.
- Better algorithm to compensate for single-axis DPAF by using multiple pixels intelligently (effective QPAF?)
- Bigger frame rate... which has rapidly diminishing rate of returns now that it's up to the rate of video capture
- Better iris AF, which is nice, but not a solve-everything solution, as sometimes you want your iris in a different place than your focus point
- Dual CFexpress Type B
- Better video codec, in-camera recording of various higher-bitrate formats
- Much better internal heat dissipation design
- A couple left-field software enhancements, such as:
- In-camera multi-frame noise reduction
- In-camera multi-frame resolution boosting (that doesn't suck)
- AF that can track birds at great distances (<2 percent of frame) against busy backgrounds
- File cookery in software to give it that 1-series look
Of all of the things above, most are unlikely, and the ones that aren't don't really make for much of a critical mass of improvement over the R3/R5.
If the resolution is bigger than the R3, I'll probably get one. I loved the R3 but for that one factor. But I'm prepared to be disappointed on that (from long practice). The great benefit of the R1 release may be the big white lens or two released alongside it. Would be super nice to get a 500mm lens that wasn't the product of teleconverter alchemy (lookin at you RF 800) or just an RF version of an older design (RF 600).