I'm curious why you think there has been a "demise of Boston". Is it really no longer a first-class "startup hub"? NYC gets more hype these days but it seems like both are great places to do a startup.
Outside biotech, it has gone from number 1 to a solid number 2 to mid-list. Seattle, Austin, Portland, NYC, and Boulder are all above it for many types of startups -- Boston has some legacy VCs, great but declining universities, and big city air travel and other infrastructure, but it is getting weaker by the day as a place to base a startup.
I don't really have time to put together statistical backing for my argument, but based on talking to a bunch of new startups in security tech, it is definitely an anti Boston trend.