I don't really understand why people are reacting so harsh, a multi-part series has a lot of benefits and a better business design to do.
The game will come out faster and sooner to the public. It would be heavily polished up the ass with great details since now they have more time to design each section of the game. Not only that, the game is also adding new content, meaning each part would have enough game play to be a complete game worth 60 bucks. Thus, a more longer and polished game than the original. In a business sense this game isn't as big as the fans believe so the game was a game changer in the past, and mostly ever gamer at the time believe so, however, the game community was quite small compared today. The community is a lot larger and making AAA games with great details has been way more expensive to make. Supply vs Demand, to make an AAA game these days without losing money, you have to be safe and knows what sells. It's better to be safe than risk it on a fan base that is not as big as it once was.
If square-enix want to take the safer path with this game, then they should because taking a risk and losing the money means they won't have the money to continue making more games. I mean, considering how disappointed people are of the news, means you deeply enjoyed of the studio and there games they make.... so why not trust them as fans and see how the series would be?
Yes there's a chance that the multi-part series could be very short, unpolished, and over priced. Not only that square-enix has been making some bad business designs the last few years.However, after seeing the game play trailer of the game and the reaction people are giving before this news, it does not look like that they're going that direction. It looks like square-enix is taking there time to make this remake as par or better than the original.