The thing is, the argument you bring is poor.
Sure, changing Gears 5 to open world is huge for a game known for its closed quarter combat. Borderlands is already an open world game. There is no real game changing structure you can bring to this outside of just making zones bigger or more interconnected, which the problem with most open world game sequels. The structure of the game already works that way, there is no need for "game changing" world mechanics here.
The thing they worked on is bring the gameplay to a better standpoint and get rid of the archaic mechanics, like Cripterion said. If you like the Borderlands franchise, it's exactly what has been asked, more guns, more options, better gunplay. Throwing anything that makes the core game "different" is divisive and could potentially be what breaks the game.
We're not at the Assassin's Creed or CoD number of sequels. We're at the 4th game in the franchise, the 3rd one developped by the main team. Even Gears needed 6 games before managing to do something out of their formula. I'd gladly take the "same old but better" approach for B3 or the next game in the franchise. If I wanted to play something else, I would turn to other loot & shoot games (which I did and I'm still back for B3).
No sorry, the argument is sound. You admit the open world change is huge for Gears.
There are ininite changes to the core gameplay that BL could potentially bring. I'm not going to list some because all that would happen here is people telling me they're bad ideas and not needed etc... and make another tangent... that doesn't change the fact the game could have a core shake up that makes the sequel feel very different.
And, again, this is not even necessary. I am simply asking IF there is anything in BL3 that has done thiis in the same way Gears 5 has.
Pretty much everyone who has responded so far has had blinders on because you think I'm trying to criticize BL3. I'm not.
Gears 5 - open world is a core change that really differentiates it from 4.
BL3 - on paper all the changes look like refinements rather than core shake ups.
Now, the latter is not inherently worse than the former. However, some who were burnt out on BL after 1, and the prequels might not find anything that convinces them to play.
Saying that, the sum of all the refinements might potentially make it feel very different. More than the sum happens.
This is just a conversation based on my curiosity. I have yet to play BL3.