Chancey289
Fake Geek Girl.
Well, of course it follows the timeline and all that, but, from what I remember it was like Metal Gear Solid: Ghost Babel, which was a game that followed the events of Metal Gear 1 and Metal Gear 2, but also took place in the same time that Metal Gear Solid for the PlayStation was supposed to be going on. In essence, it was a replacement for MGS1.
Ghost Babel was just a "what-if" game that followed the events of Metal Gear 1 and 2 and even had you returning to Galuade and the old Outer Heaven base. In the same vain, Metal Gear Rising follows the events of MGS4, but is otherwise not technically part of the canon, because it's just a "what-if" game. That's what I mean - I'm not sure if I'm being clear or not :x
Ghost Babel though is a side story that does contradict which is basically the core canon. It's the core Metal Gear lore so maybe that is just a mistake on their part. *shrugs* it's up in the air really.
MGR however doesn't really have anything going against it like that because being where it is in this timeline it's its own thing but can still tie in to the Metal Gear canon without interfering with things already established.
MGS 4 really concluded the story so you can't go in to the future really. (Except if P* and Konami just wants to say f#ck all to Raiden's retirement and feed him back on the battlefield like they did.) It gave the characters their resolutions, it answered all the lingering questions, and Snake was dying. You can really only now dive in to the past which is what Phantom Pain is doing again.