Honestly, Rebirth should've been the more open linear style game, and whatever part 3 is called should be open world. Considering when you get the highwind, that is when exploration really opens up in the original.

There is so much left to explore in the REtrilogy, it makes more sense to have the last game be the biggest and most explorable game in the series. I understand not having time to dedicate to a game but, we can't expect devs to cater to us personally.