I think it depends on whether the name is meant to be a reference to Goranger (FiveRanger), seeing as that show also had a constellation motif.
Well they're only mentioning it now because details about the show are being released. It doesn't mean the collab couldn't have been a year or more ago.
I think they mean making any changes that might help the inevitable Power Rangers adaptation in the American market without affecting Sentai (which targets a younger age-range).
For example, IIRC the action figures are typically the best-selling toys in the States, but not so popular in Japan (where the mecha often sell better). Kyuranger has more heroes whose suits have more varied (and yes, less pajama-like) designs. Maybe the thinking is that this is more helpful to the PR toyline than to Sentai's, but shouldn't be a change that hurts sales in Japan?
I think it means the last option. You should be able to recognise that it's part of the franchise, but they should still be distinctive and not just "a Sentai".