I guess my Google search skills are not up to par. Trying to see what Canon is doing about DSLR. I was looking at picking up an 80d or 90d later in the year (used) but was seeing that there will be nothing after the 90d. I assume EF-M stuff will not get a lot of support just for lack of accessories so I figure they will offer something in the R line. I hope it has the regular DSLR feel but is mirrorless. I do like my M50 and I got used to the size of it now. I guess there are no rumors floating around with a time frame yet? I would hate to get a used 80d/90d then 2 months later the equivalent R camera gets announced. But for product shots, I will not need the latest and greatest.
I think you'd be fine to go forward if you plan is 80d or 90d, the 80d had a 3.5 year window, the 90d is only 2 years into its life. I would not expect another after for a year or longer if at all.
It was hard for me to to spring for the 77D body I bought from Digital Goja about two years ago and since I really don't have a lot of experience with this one I am going to fore go any new equipment for now. For me to go to a new format such as full frame and mirror less l would have to get the appropriate lenses which would be quite an outlay even at budget minded ones. I have to learn a lot before I could even justify a 90D.
Well, if you have EF lenses you can get a RF to EF adapter and use your EF lenses. Your 18-400 would prob be ab issues to adapt to something new. I picked up an R and really like it. I do miss the mirror slap though. Having shot 35mm film for a while, this was not much of an adjustment.