I started GTFS Data Exchange in 2008 to encourage adoption of the GTFS specification when barely a dozen transit agencies were sharing schedule data. Since then, much has changed as there are over a thousand agencies from almost every country around the world publishing GTFS data.
Recently the Secretary of the US DOT wrote a letter advocating broad GTFS contribution and a national registry of GTFS, coming one step shy of requiring it from all agencies. The World Bank has also heavily advocated and assisted international adoption of GTFS. That these sorts of organizations have a default expectation of open schedule data was unthinkable in 2008. I'm proud of all the transit community has accomplished, and excited about what's next. Closing gtfs-data-exchange will pave the way for the next chapter of open transit data.
https://transit.land/ has steadily been growing as a reference spot for worldwide GTFS data, and the spot for transit agencies to connect with developers. It is also built to expose schedule data from a single consistent database which makes it even easier for developers to access schedule information. Most importantly though, Transitland has a corporate sponsor Mapzen, so developers can rely on it whereas gtfs-data-exchange has always been a side project, intermittently available and sometimes neglected.
http://transitfeeds.com/ also has a comprehensive list of GTFS feeds, and is built on a much more open and transparent community contribution process via Github.
Q: Where should I register a transit agency's feed?
A: https://transit.land/feed-registry/ and https://github.com/TransitFeeds/TransitFeeds-Public/issues
Q: What will happen to historical feeds on gtfs-data-exchange? A: Historic feed archive will be available for research via AWS S3 "requestor pays" policy. The dataset is currently 13k files totaling 93G from 2008 onward. Contact me if you'd like access.
If you have any specific questions about this transitio, reach out to me @jehiah