Naughty Dog certainly stuck to the original formula, also adding in a new open world aspect half way into the game. (cultureofgaming.com)
Kojima has said before the areas in The Phantom Pain will be much larger, with Ground Zeroes serving as a prologue to give players a chance to adapt to the new open world aspect of the game. (metalgearinformer.com)
When done incorrectly you end up with a title like Defiance that tried to make a big deal out of the MMO and open world aspects while getting the loot and character progress elements completely wrong. (massivelyop.com)