There are a number of potential advantages;
1) AF points covering a much larger proportion of the frame. Yes
2) 'Zero blackout' from raising / lowering the mirror (this does require a very fast sensor readout, currently only the A9 does this) Not enough of an advantage for me.
3) Higher FPS rates as no moving parts to worry about. Yes but will it only be with native lenses. Sony A9 with a meta bones adaptor halves the frame rate.
4) Totally silent shooting - which can be a benefit in some situations (actually, any situation in which extraneous noise is a disadvantage) Never found it a problem but wouldn’t knock it.
additionally an EVF has advantages (but you could fit an EVF to a DSLR if you rally wanted to)
1) EVF allows you to see changes to settings directly. Not sure that’s an advantage.
2) EVF allows you to review images - avoiding 'bright light on rear display' issues, and also meaning you can shoot, review, shoot without moving the camera from your eye I review images only for critical focus so don’t see that as an advantage.
3) Additional information overlay - you already have some overlay within OVF, but EVF allows more flexibility to add things like live histogram, virtual levels, etc.