I thought I'd go over the rumors and confirmations of the rules in Gokaiger.
When it was first rumored in September that the 2011 Super Sentai was going to commemorate the 35th anniversary and have Rangers that transform into Rangers, fans instantly thought of Kamen Rider Decade, which celebrate 10 years (since the show was off the air for a while before 2000) and the hero transformed into past heroes. In Decade, the heroes traveled from dimension to dimension, each dimension covered one series that lasted one year (I'm writing this people who may not know). Then as soon as we got more info, that they were pirates and they traveled in a pirate ship, fans assumed they would go to different dimensions representing each Sentai or go to a 'Sentai sea' and go to each island and visit old members.
But it has now been established (in the first episode) that the Gokaiger are aliens from another planet and just arrived to Earth. And there was a Legendary War that including all the Sentai (teams), but did exclude some members that may not be that important (BullBlack, Signalman, Ninjaman, MagiMother to name a few). In one ad, it said the Gokaiger would transform into 200 heroes. But it now seems they are only transforming into Rangers that were in the war. Because if you count the sixth rangers Gokai Silver will turn into, that accounts all the heroes that were in the war. 172 Ranger Keys (of the teams of 3 to 5 including Gokaiger) plus the 16 Gokai Silver has makes 188 and we know
182 heroes were in the Legendary War. 182 past heroes plus 6 Goklaiger make 188. In the War, they all lost their powers.
From Hyper Hobby:"The 5 Goseigers, with their powers, appears before the Gokaigers. Black Cross (villains of Goranger) revives from hell in order to take revenge on the Super Sentai teams. 199 Heroes will appear in this Legend War. However, 182 Sentai Heroes + the 5 Gokaigers does not equate to 199. Who could the remaining heroes be!?"In Episode 5, Doggie Krueger will come around. Maybe he still has his power of DekaMaster. So we might see 12 other heroes in the movie. And plus 1 is GokaiSilver to be 200. So now we know there will be 200.
Thanks to subtitles some sites have done, we know that the Gokaiger barely even knew who the past Super Sentai were. Aka Red gave Marvelous the chest with the Ranger Keys and the Mobirates and Sword. He rounded his team up and they know they can use other powers but thats all they know and seem not to care.
Kai (MagiRed) appeared in Episode 3. Past heroes will return, they have no powers but still fight and have some sort of power. Kai used Frajiel, his Sky Saint. It seems he was there to test them. Their parrot robot Navi will give them clues and it seems one or more past heroes will 'test' the Gokaiger or lead them to some sort of treasure. The Gokaiger didn't give Kai back his powers, maybe they will at the end of the series. It seems they will transform into the team the past hero guest represents and then show off their individual powers and gain some sort of knowledge or power.
Kai tells them that if they master all 34 teams' powers, they will be able to gain the universe's greatest treasure. So, they can change into past heroes but the goal is mastery. Another thing is that they transformed into Magiranger in Episode 1 and then in Episode 3 but more significantly. In Episode 2, they became Dekaranger and we know in Episode 5 they will meet some Dekaranger and most likely transform into Dekaranger for a longer period to be highlighted. And it is rumored Jan of Gekiranger will appear in Episode 7 and we know from the Ep4 preview that they will transform into Gekiranger. In Decade, Decade would become a past rider in a new world after gaining their powers in the last world/episode. So here seems to be the opposite. They will briefly transform into a team and a few episodes later they meet a member. That seems to be a pattern for now.
Another rule is the Gokaiger can use any key they want and transform into any color they want, they don't have to go by their color or position. But when all 5 transform into one team, they do have to be assigned to their analog/counterpart. I like when they transform into past heroes of just one color, it confuses the enemy is sort of a 'Forever Red' of other colors.
And their auxiliary mecha seem to come when they learned a lesson or found a 'inner treasure.' Magi Dragon popped out of the 'treasure chest' compartments of the robo. The rumor that the robo would switch heads of old robos seem to not be true for now. Who knows, it might happen later. And villains becoming past villains seems untrue for now as well. Their villains seem to have no connection to past villains.