Honestly, Third Avenue has already been degraded into a glorified service alley. By my count, there are only four buildings which predominantly front on it.
1.
Point Park's Patterson building. Although it has a different parcel/owner, it seems like it's essentially the back side of the Red Cross building on Boulevard of the Allies
2.
The PITC building, which is right next to the demolished structure. Note it has a parking gap on its other side, meaning the block is not intact. Also it's connected to a building on Fourth Avenue, which has the same owners, so it's unclear if the two buildings are truly separate at this point.
3.
This small and unremarkable office building. Looks like it might have been reskinned during the mid 20th century. I find it hard to believe it was born that ugly.
4.
The Chinatown Inn's two buildings. Technically the second building runs all the way to Court Place, but it's clear that is considered the "alley side" by the business.
There are a few more buildings which mainly face on the next block (or around the corner) but have an attractive rear or side facade - in a few cases much more attractive where the front has been remuddled but the back is left untouched. Nonetheless, Third Avenue is for the most part not too different from Exchange Way these days, and does not have a reasonable chance of becoming a decent urban street again.
First Avenue is where area preservation should be focused.