Not accurate if you base in the DC SFRA, any airport that has a tower, any airport within or butt up against the surface area of an airport with a tower, operating in or near a VIP TFR, operating near or in a stadium TFR, and so forth.
Where I live and where I used to base the plane it was mandatory (SFRA/FRZ). And for practical travel on the east coast and parts of the gulf coast (and parts of California), not being able to go IFR means not going. I suppose it will boost sport pilot because flying then becomes just recreational.
And what happens if/when there is another event that closes airspace to everything except IFR traffic?
Yes, there will be more scud running, but ADSB will make aircraft easy to identify, and it's entirely possible that the FAA will put more restrictions on VFR flight ('for safety purposes').
Nope, no impact at all