I agree the dont have to be bigger just more ergonomic. Besides we are talking 1-2 cm difference for any body out there, that means they are as small as practicality would allow anyway.
IMO we'll see EPL-1, GH1 type of EVIL first.
And yes going EVIL in DSLR form would not have any size advantage, but as said that is not really wanted, from ergonomic point of view.
And there is one more issue, IMO. Dont mess with DSLr users. If you want to keep them happy and shooting your gear, you must offer them Quality (EVF) with great tech and features, good build and compatibility with EF mount.
They won't press canon for size, much. (well maybe a smaller FF body with HD EVF wouldnt hurt)