... Leica lenses are"smaller" due to there is NO AF and NO electronically controlled apertute. Look at the 4/3 lenses, they are even bigger than the Leica lenses.
Reality has no place on a foto-forum
The only FF "mirrorless"exists is LEICA M9. It is a $9K camera. Let us look back into history. In the late 60's the price of the best Canon Range finder camera is about 80% of Leica M3. So if we strap the curve, A Canon M9 comparable mirror from Canon will be about $6k to $7K. Will you buy a 1D-X or the Mirrorless.
The way Canon has been pricing things lately, I'd expect 90% to be closer to the truth
If the FF mirrorless can be built so easily and cheaply,whay nobody is doing it???
Sony fans are clamoring for a Full Frame NEX 9 too. But there doesn't seem to be a glimmer of hope there either.