BART plans a billion dollar bandaid by digging out the other side of the station to allow boarding from both sides of the tunnel. But that billion dollars doesn't buy any additional tracks, just an extra exit from the sides of the trains.
Even the new 6+ billion dollar transit center is only going to have 3 platforms and 6 tracks for Caltrain and HSR. In comparison, Penn Station has 11 platforms & 21 tracks.
What the bay area needs is a regional government that could set reasonable housing and transit policy instead of dozens of disjointed communities that only want office space and no housing and stand in the way of transit improvements.
There's no single solution that will solve the housing problem -- it'll take more housing closer to jobs, and better transit. (I purposely left out traffic improvements since that's a short-term bandaid)
China is spending trillions on infrastructure and trains and we whine about 6b for a huge train station in the center of a hundred year old city, while we give $1.5 trillion tax cuts to corporations