San Francisco suffers from too many small town self-inflicted political wounds. While the Central Subway will open in a couple of years with it's new subway and light rail cars, it'll likely be the last one for us, perhaps even for our children. Political power brokers, such Willie Brown and the late-Rose Pak, only rolled in their power to give Chinatown a replacement for the Central Freeway that was torn down after the 89 quake.
Existing SFCTA members, which are also the Board of Supervisors, constantly squander transportation funds. Millions have been poured into funding pet political projects, such as free muni rides for youth and seniors, making Muni a system of handouts instead of pulling free ride funding from the Feds or the general fund. The latest axe swing was to delay the DTX, the Caltrain subway to the Transbay Tower, which the voters prioritized in 1999.
The existing anti-transit, anti-growth cabal of Kim, Peskin, Campos, Yee, Mar, and Avalos have been able to grab too much power, and will always vote to side with NIMBYs (Not in My Back Yard) over modern urban growth and planning. Even the next cohort of supervisors will hold the same values, because the voters will put similar people into power once they term out, cutting more into the city's progress as a metropolitan powerhouse.
My educated predictions on this chart are: We'll see Geary BRT, Geneva BRT, 19th Ave Rapid, and the M extension to Park Merced. Maybe some new signals and bike lanes. That's it.
The SFMTA's 20 year vision does not include any subway or rail extensions otherwise. I have asked Nick Josefowitz, who's district would include a theoretical BART extension under Geary, and he says BART is too far behind on maintenance to even consider such an idea.