In the Tenderloin proper, a block has been chopped off on each side. On the west, gentrification has partially advanced to Polk St, with a "globally inspired rotisserie" across from Royal Liquors. The "Polk Gulch" area, once home to rent boys and trannies, is almost gone. On the south edge, at Market, since Twitter moved into the old fashion center (SF never had much of a fashion industry; the other fashion center building, in SOMA converted to Sega, then Zynga), the "mid market" dump of an area is rapidly being rebuilt. There are still SRO hotels on that part of Market, but two of the three strip clubs have closed.
In the heart of the Tenderloin, around Glide, buildings are being rebuilt. The SRO hotels owned by nonprofits remain, but they're being surrounded by rebuilt buildings and hipster restaurants. Some of the SRO hotels are getting upgrades.
It's going. Slowly, but it's going.