I think it’ll stick pretty close for the most part. What I don’t know is how they’re going to do Vincent and Cid justice in their storylines. There’s just so much to cover all around.
My take is this: starts with party climbing toward Icicle Village, spend some backstory on Dr. Gast and Ifalna similar in scope maybe to the Neiblelheim flashback. Snowboard. Get to the Northern Crater relatively early – THAT scene happens and releases the true Weapons. Everything proceeds as normal through Cloud and Tifa falling into Lifestream after Ultima attacks. Then what I don’t know is will the game abandon the two of them for a significant amount of time while the others get to Rocket Town, go to Wutai, a good portion of Vincent’s backstory. I don’t remember enough about what happens in these sections to know if they could go without Cloud being present. I think obviously he’d need to be back before the quest for the Huge Materia begins, which partly takes place in Rocket Town. But then that still leaves the underwater reactor, Fort Condor (I could see this being cut), I think the Knights of the Round will be a huge part of the main storyline in this, then obviously the turn to Midgar. There is just SO much to do. And who knows where alternate timeline Zack fits in with this.
But I think it’ll stay relatively on the rails up until the final but in Northern Crater, then all bets are off.