This GDC I strongly felt there's a large movement of young indies that I know nothing about.— ColinNorthway (@ColinNorthway) March 8, 2017
Is there a cultural nexus I can visit?
As Colin implies, I suspect there is actually no real equivalent of a central "cultural nexus" like TIGSource today. In fact, I've been in on the ground floor of several attempts to make new TIGSource-likes, such as Super Friendship Club and Makega.me, and both of them eventually petered-out in the end for one reason or another. I'm still not sure why, but maybe it's possible that internet forums are a poor fit for what we need these days?
The indie games moment arrived, and has now stabilized into a satellite commercial industry of the game industry. We don't need a central place like TIGSource to imagine it or to advocate for indies to exist. Commercially indie showcase events like Day of the Devs, The MIX, and Indie Megabooth have been been running for a while and will probably keep running.
Today, what would be a public game organization's "mission" now? Everyone has so many different needs and concerns. It's kind of absurd that we even imagined one global "public" that TIGSource was supposed to serve? Local games community problems here in New York City are very different from local problems in, say, Pittsburgh or Capetown or Teheran or Shanghai. One single internet place cannot hope to address all of that.
Many local communities and friend groups have Slacks and chatrooms, but most of these are private and unlisted -- they don't have the "public" face that TIGSource provides / provided. What, are you going to invite Colin Northway to your Slack now? Even if he accepted the invitation, he likely wouldn't stay very long, because Slack requires constant (hourly? minute-by-minute?) engagement and labor to function as a community -- and it'd still be difficult for Colin to understand the tone of your Slack, or what it's really about.
To me, a public games culture should serve two functions: (1) help a local community cohere together, and (2) articulate that community's voice(s) and concerns to the rest of the world.