The way I see it, there can be three ways:

1. The game will be exclusive until all parts are released (so a very long exclusivity period);

2. Every single part will be exclusive to PS4 at the release. The episodes will come out to different platforms before the new one is made;

3. Only the first episode will be temporary exclusive.

What do you think? I think the second way is more likely to happen, but who knows? They could take the first method and in that case it would be a huge deal, a full exclusive essentialy. 

Why would FFVII be exclusive? I'm sure it will be avalible for PC, and maybe the XBone (and probably NX), Square will want every possible consumer on board, and FFVII is a popular enough game to not need any exclusivity deals.

That's actually a really good question. I have no idea. Depends on what kind of deal they made. If the deal was for the entire game and the idea of splitting it happened afterwards, Sony could just insist that it needs to stay exclusive until every episode is released.

Probably 1)
It is not yet being made for any other system so I expect the porting won't begin until almost all the episodes are done

We don't even know what the nature of the episodic release schedule, so answering this is pretty much impossible.

The game will come out first on PS4, so it will be exclusive, we just don't know for how long and in what way. That's why this thread exists.

That's a good point, if they want to release each episode faster they can't focus on other systems.

Agreed. Porting is easier when you have the whole thing...

Not to mention it also allows them to keep tabs on the viability of ports. If the episodes sell nicely, it's easier for them to port the game than a flop...

I think that's the whole point of their exclusivity deal. If it does good on the largest community, it will be decent in others.

Timed exclusive.

I think just 1 part will be released first in PS4 then all other parts will be released at the same time. It was just a sneaky way of making it sound better than what it actually is.