I do know Canon reps agree the R is somewhat of a first attempt, and more designed from a 'we'll take a dslr and take the mirror out' point of view instead of designing from the front up, and lacking in some area's. This was said a few weeks ago during a CPS meeting here in the Netherlands. They agree the R is more in the 6D-line. They said they also know the pressure of Sony is high, and they also said 'of course we can't say a lot, 'cause we'll get fired', but 2020 is going to be very busy and very interesting, and people considering a switch might want to wait a little while.
So, I wouldn't be surprised if we see indeed a truck load of bodies coming our way this year.
A mark 2 could give us: improved ergonomics (for instance, that AF-on button is totally in the wrong place), dual card slots, IBIS, more features (think: multiple AF servo cases like the 5D4), more buttons to assign (think: dedicated buttons for very specific AF cases, like the 5D4). So, plenty to work with I'd say.