What else is there to innovate in DSLR? MILC still has plenty of room to improve that's why we are seeing more progress more quickly there. The progression will slow down soon enough.
I certainly can't think of any way that DSLRs can improve other than marginal upgrades. It's dead-end tech as far as I am concerned. The mirror and prism system was developed to let people see through their lenses to better frame their shots. It was the best solution at the time, but mirrorless is a far better solution, because it not only lets you see through your lens, but also see through your camera body, so there's no question about what your shot will look like.
I really want to see Canon and Nikon get into the mirrorless game. It's not good for the market if Sony is the only player in the full frame mirrorless category. Even in APS-C, the only rival is Fuji, who are awesome, but it's hard to call them a huge player in the market.
Honestly, I think the A9 that recently came out represents a tipping point where mirrorless cameras no longer have to carry compromises compared to DSLRs. Auto-focusing tech was really the last bastion where DSLRs were objectively superior, but that's no longer the case and I think we will continue to see mirrorless cameras improve in this realm, skyrocketing past DSLR tech.
There is still so much room for innovating in the mirrorless realm. It's unquestionably the future of digital cameras. DSLRs won't disappear anytime soon, but they are definitely going the way of the film camera. I would love to see more variety in bodies. If Canon and Nikon could put out some bodies that are able to take advantage of their massive lens lineups, then that would be amazing.
MILC has definitely reached the point where I start to recommend it to people new to photography. Many features will surpass DSLR (and many already are) just because it being able to analyze the image in real time. I'll always have a DSLR because I can't stand EVF or don't need its features in various situations. I also don't trust weather sealing on MILC. And my MILC will always only have prime/pancake lenses in order to actually take advantage of having a smaller body. I own Pentax DSLR so I already have to make up the AF-C deficiency using techniques, which I think are good to have, so I honestly don't care for AF that much as long as I can override the focus without having to switch to MF mode on the lens/camera. I always tell people: There are plenty of BIF images captured by people on film cameras with MF. I already have way better tool than they did so there's no reason why I can't at least match what they could do.
This honestly reads like "well, the tech isn't in my camera of choice, so I don't need it!" That's fine and all. If people are happy with their gear and the results they are getting from them then there's no need for them to change to anything else, but I also don't understand the desire to argue against better tech, which is the impression I got.
For example, if AF-C deficiencies did not exist and all cameras had 1,000+ ultra-fast auto-focus points covering 100% of the frame with various options for what to prioritize, etc. would you so value those "techniques" you talk about? When it comes to overriding the autofocus, don't most camera bodies have an AF button that can either be pressed to hold or clicked to toggle auto-focus on and off for quick access to manual focus whe nyou need it? No need to flip a switch on the lens itself or take your eye away from the viewfinder.
Personally, I can't understand the appreciation of an optical viewfinder, but that's probably like arguing with someone who swears by film and film only about the merits of digital. Seems like a lot of it is about "feeling" and what the person is used to.
