Network effects are a (nonlinear) function of network size. The bay area is limited by local zoning ordinances and can't scale much larger. There's only so many locals to displace and new construction happens at a snail's pace. New York has a much larger scale already, so at this rate it's just a matter of time until New York overcomes the network effects that the bay area currently enjoys.

The factors that could keep the bay area dominant are:

(1) Rapid densification and development of the region pushing down prices and attracting newcomers (not likely)

(2) A tech recession halts the expansion of the sector and potentially begins a phase of consolidation

(3) A paradigm shift towards remote work