Not a lot. Cincinnati, despite being a sort of Midwest food mecca, has a dearth of BBQ places. Montgomery Inn (mostly ribs on the bone) is the clear favorite (3 locations). Pit To Plate in North College Hill is a little Mom-and-Pop place that's pretty authentic. I'm sure there are others. Other than the Montgomery Inn, I'm probably more likely to get BBQ in North Carolina (6 hrs away) than Cincy.
Walt's had a fairly loyal clientele over the years--I can still remember riding by there many times, even back to the late 50's and seeing them grilling ribs in that unique little out building in front--it seemed so unusual.
I'm not altogether uncertain from what I've heard that even tho it is "closing", that someone outside the Melton family will buy it and re-open it. Or it could become something similar (e.g. a reception hall, etc.) It's been there way too long to just disappear completely.
400 Buttermilk Pike Ste 200, Lakeside Park, KY 41017