"With the R3 you can shoot a few thousand frames in a few seconds (which I own)"
2000 shots at 30 fps = 67 seconds - "a few thousand frames in a few minutes" is the correct maths. A couple of years ago some would have laughed at the thought of 2000 30 Mpx shots in a minute and they were just as wrong as you are laughing at 30x100 megapixels in a second. I don 't want 30x100 megapixels in a second, but some do and that's their privilege and you have no right to mock them.
Birdshooter is correct, people expecting 100MP at 30fps is totally unrealistic NOW, the consumer technology just does not support that! The logic associated with that expectation is quite messed up, since anyone wanting to photograph birds must do that with the current technology, which is perfectly doable. Bird photography has been carried out in the past with lower megapixel bodies and slower photo burst rates than the ones available now, so a 100MP 30fps body is definitely not a prerequisite for successful bird photography. Following the logic of those unrealistic expectations, people can wait ten or twenty years until that technology arrives to photograph birds, or they can go out and give it a go with the gear they have or that is presently available. They might even enjoy themselves!
The way I read it, the expectation 100MP at 30fps doesn't say "I want to photograph birds", it just says "I want to own very expensive, cutting edge technology that is capable of photographing birds". The latter is a 'gear head' perspective, which is fine for people who love gear for gear's sake, but it's important to distinguish that from the needs of people who want to enjoy time in nature photographing birds. New technology makes bird photography easier, and it is an incremental process. The way it's written sounds like it's a binary situation where a certain threshold of technology specifications exist (100MP at 30fps), where no bird photography is possible with anything below that. I can imagine all the National Geographic teams worldwide throwing their arms up in exasperation and telling their employer that they can't possibly take any bird photos until cameras can shoot 100MP at 30fps!
To push the technology envelope, why stop at 100MP at 30fps in a standard camera body? Dream big! How about an AI motion detector tracking system, this technology already exists on advanced home security camera systems. Tripod mount the system, point it in the required direction, and let it rip. With 250Mp and a burst rate of 50 fps, you can just select the desired frame and crop in drastically to choose the image. Welcome to the brave new world of hand-off bird photography, where the bulk of the work is done in post (over many weeks), which so many desk jockeys love!
To anyone that says that they need 100MP at 30fps to photograph birds, my question would be "What is stopping you now?". Realistically, it's probably budget if a very high standard of image quality is expected, unless the limiting factor is something not related to gear acquisition, such as training. What is certain is that if a camera boidy that can do100MP at 30fps is released, it won't be cheap, and would remain very expensive for a very long time!