[JJ_SO]

....... to have as high an IQ as possible .... as in a VF image, that doesn't look like an EVF  ...... or at least ... near to that.

If you ignore that every OVF also is altering the "reality" you demand an EVF to be much better than the gros of the already existing OVFs.

Question is, what are you preferring: a picture coming as close as possible to the end-result - then it's an EVF. 
Why? Because 

• lens correction is already shown, 
  
• it shows close to 100% of the sensor area (average OVFs show like 93-95 %), 
  
• white balance, 
  
• JPG-profiles, 
  
• sharpness, 
  
• even lens flare which are a result of sensor reflection (and no OVF will ever show this flaw of the ML system - but then, I can't remember any DSLR being that bad in terms of sensor reflections like I've seen with some ML systems dues to shorter flange distance)*
  
• medium strong ND filters don't make the OVF useless, as there's still enough amplification to allow focusing
  
• You also see the troubles based on flickering LEDs or incandescent lights - something you'll never see  in an OVF, but very much on the pictures - and just too late to repeat the shot.
  

if you prefer an OVF, you basically 

• save electrical energy and increase battery life massively
  
• see all optical flaws of a lens uncorrected
  
• see a de-cluttered finder picture without dozens of icons as most informations are displayed in extra display lines
  
• can't see the proper focusing if you have a lens which needs a lot of AFMA or have a camera with a  slightly misaligned matte screen or mirror
  
• don't see problems based on low frequency refresh rates or low resolution EVF
  

All finders are a compromise and no finder system shows the final result, the real dynamic-range of f-stops you can get out of a picture or the ammount of motion blurr (on most EVFs). So, this part is correct, there still is room for development - but all this added functionality can't be delivered by an OVF.

* this part is a systemic problem of ML and short flange distances. Not caused by EVF and also not improved by using an OVF instead (I have that on two Sigma Merrils, and the dp0 quattro can be quite nasty in this aspect)