Take this for example.
FFXIII 2009, FFXIII-2 2011, Lightning Returns FFXIII 2013. 3 parts, all released within 4 years.
However I think as FF7R being a bigger project, with a big budget, and a large development team, I think it's going to be a lot bigger than RDR2, because the world map is pretty much planet size.
FF13 (and it's 2 sequels) isn't the same game split over 3 parts. People have got to stop using that as an example. It's a game with 2 sequels that sold no where near the numbers of the first. Each game has returning characters and theme but gameplay is different, controllable characters are different and the stories are different.
Can you imagine if the first FF7R part sold 10 million then the next only sold 4 million? It would be considered an utter failure. Then the finale only sold 2?