I'm sorry, but I would HATE the american companies for ever if they brought Gokaiger over. We don't have NEARLY enough seasons of Sentai for it to work properly.
FYI PR has adapted more than half of the sentai seasons so that 'not having NEARLY enough seasons' is false. They have 20 seasons to make ranger keys out of, and all of the auxilary mechas used from the ultimate powers are from Post zyuranger seasons (except for gorangers mecha in the movie) so there shouldn't be any problems.
The way I see it, considering MMPR ran for 3 seasons, it should have 3 ultimate powers.
One would be Ninjor (since it doesn't kinda really work for the alien rangers unless they say Ninjor originally trained them or something)
One would be Tommy giving the 2nd ultimate power for Gokaisilver's adaptation
and lastly the final ultimate power could be Titanus, since, if I recall correctly, it was never destroyed.
That's just my idea anyway.
Also for the Turbo tribute episode I'm kinda hoping they keep with the humor (tho I understand why they would decide not to do it since turbo wasn't really comedy focused), with the rangers morphing into the In Space rangers, only for TJ to say that he wanted the other team (aka the team he was the leader in) so they THEN morph into Turbo.