An interesting thought occured to me today. After playing Blacklight Retribution on PS4 I saw distinct similarities to MGO, as teams would have hubs where they could exchange points they had earned in battle for weapons and/or support, and similarities to Titanfall, the game allows you to call in a hardened battlesuit equipped with miniguns and a railgun.
Given the Drebin Points system that was present in MGS4's online component, I believe it would be interesting (and not all that far-fetched) to assume that similar gameplay elements may make an appearance in The Phantom Pain's online component. Racking up points through the neutralisation of enemies or completion of objectives for particularly powerful or favoured weapons in return, or...
Access to Metal Gears.
Now I don't mean big, badass Metal Gears like REX, RAY or Peace Walker I mean a kind of Metal Gear that looks similar to what can be seen at the end of one of the for The Phantom Pain. You'll notice it's not gargantuan like the Metal Gears from previous games (bar the Mk.II/III), so it's plausible to say it could be moved into a battle situation much easier. For this reason, I reckon that there's a great possibility we could see this kind of gameplay integrated into the next Metal Gear Online.