No one can forcast what exactly will happen the next few years. I agree with Michael that the writing is on the wall.
In your comparison you specifically start talking about very expensive systems that weigh a lot and are not mainstream and never have been so. Mainstream to me is a system that is sold the most. Currently that is an APS-c DSLR system. I can see that change withtin 5 years in some mirrorless form of m43 and or APS-c and or some other, to be developed largish sensor. The mainstream in my opinion will be mirrorless and (therefor) will have and EVF. The biggest hurdle in my view is not the high ISO performance, not the AF speed nor the IQ in total. It is really good and good enough for the mainstream. What is holding it back other than sentiments is the problem with action shooting. If EVFs can (they will) overcome that one (processorspeed will be important of course), a lot of people will get rid of APS-c DSLRs and their large lenses. I am convinced of that.
In your comparison you specifically start talking about very expensive systems that weigh a lot and are not mainstream and never have been so. Mainstream to me is a system that is sold the most. Currently that is an APS-c DSLR system. I can see that change withtin 5 years in some mirrorless form of m43 and or APS-c and or some other, to be developed largish sensor. The mainstream in my opinion will be mirrorless and (therefor) will have and EVF. The biggest hurdle in my view is not the high ISO performance, not the AF speed nor the IQ in total. It is really good and good enough for the mainstream. What is holding it back other than sentiments is the problem with action shooting. If EVFs can (they will) overcome that one (processorspeed will be important of course), a lot of people will get rid of APS-c DSLRs and their large lenses. I am convinced of that.