I'm actually old enough to remember 8th Avenue from when I was a kid. Back then, the street was primarily residential. It also did not connect into downtown at that time. The Summit connection was only done, once I-30 was widened and re-routed to the south. The commercial portions of the street were located at the intersections. The first major commercial intersection was at Rosedale, but I think it actually had some residential at that intersection. Then there was another corner of commercial at Magnolia. The next was at the blocks around W. Allen and Park Place. A small commercial/industrial area was at Windsor Place/W. Arlington. From that point south was the old Frisco Railroad Yards on the west side of the street. There was no development, no sidewalks, nothing there until Stanley intersected with Cleburne Road. Going back specifically to 8th Avenue, there wasn't any commercial development on the east side of the street south of the commercial area at Windsor/Arlington. Technically, 8th Avenue continues due south, just after W. Cantey where Cleburne Road splits off. At W. Berry, there were the 1920s-50s commercial buildings that lined Berry, but they didn't front along 8th. South of Berry, 8th does continue on and finally ends at W. Seminary Dr., but changes name to James Ave., which is actually a parallel street one block to the west through Ryan Place and Rosemont. James Ave. continues on south with underutilized commercial. Crowley Rd. splits from James and becomes a part of the State Farm to Market Road System (FM 731). FM 731 terminates half way between Burleson and Cleburne at FM 917. Between Berry and Seminary, 8th is not continuous, because it is separated by the BNSF Railway. Since it is not a through street between Berry and Seminary, 8th is entirely residential in this area, with the exception of some small industrial between W. Ripy and W. Butler, which is right around the railroad right-of-way.
I really don't think 8th Ave. will become more of a walkable urban place south of the commercial area at Allen and Park Place, mainly due to the active historic districts and neigbhorhood associations. This is just my opinion, but I have lived in the area all of my life, and I know the neighborhoods and the residents pretty well.