Well, The Gokaigers flagrantly introduced themselves to the world in the first episode.edriel13 wrote:
Ep17: (this is the 1st episode that i raised my question about Gai's knowledge) Gai knows all of the Gokaigers/alteregos, even they havent transformed in public,.
How did Gai know all of this if Super Sentais in the past didn't transform publicly in the Super Sentai world?? Did they have a wiki for Super Sentai in the Super Sentai World??
Granted that group of people wasn't very big, but they could have told the news or something.
As for the rest, remember that it is tradition for a Sentai to lose their powers during the final arc of their show.
That is one opportunity for a team's identities to be revealed, and there is an unknown amount of possibilities after their show is over.
Plus all of their identities up to Magiranger were already known by at least some people by the time of Boukenger.(As shown in the vs special)
edit: Just thought of something else, the Super Sentai world has internets. I'm sure all sorts of rumors would end up on them.