I don't think the A1 will affect the sales of the R5 and R6 very much at all. First, the differences in the cameras (R5 and A1) specs are really very small. One can easily argue, for instance, that the R5's video specs are actually better than those of the A1. 4:2:2, full DCI resolution and format, about the same heat limits or maybe even better, higher resolution 4k HQ and HQ out to external recorders, upcoming firmware bringing out Cinema Raw Light and many other aspects of video performance are better. The 30FPS for stills of the A1 come with picture quality losses compared to Canon's 20 FPS performances, and when the quality of the Sony is at the same level as the R5, the max frame rate for the A1 is also 20 FPS. The extra 5 MP of the Sony is insignificant, and the ergos of the R5 and flip screen are better, and the headline RF lenses are so far unmatched.
The only potential advantages for the A1 that I can see right now are a more detailed viewfinder at a higher frame rate, which may be significant in use, faster synch speed for flash in electronic or mechanical shutter, the pixel shift high res stills function (can be implemented in future firmware in the R5), and a faster electronic shutter actuation in general, which may aid in reducing image distortion in video mode and in panning action in stills photography - the extent to which is currently not precisely known. Considering that the A1 costs $6500.00 and the R5 costs $3800.00, the R5 looks like a near match or better, with some advantages going to the R5 and most of the advantages for the A1 being quite minor, while the price for the R5 makes it look like the bargain of the year compared to the Sony.
Overall, when the smoke of the Sony promo fever and its advocates clears, my estimation is that Sony's new camera will be a wonderful but extremely expensive option for existing Sony customers already invested in their lenses, but a quite meek and underwhelming response to the R5 that will hardly effect the popularity of the R5 among current Canon users and users of other brands considering switching to Canon for the R5.