That's true, however since i messed several times with ggpo over past few years it's not that hard to build around it. On the other hand it's probably very hard to integrate it with a game that wasn't designed from the start with ggpo in mind.
Well, that's the core issue. People say PUT GGPO IN IT when we're talking about a sequel that uses 50% or more resources from its predecessor. You simply can't just take Tekken or MK or Virtua Fighter and just drop ggpo on it like its hot. You'd need to tear said game apart and rebuild it. This is not a realistic sentiment for most sequels / expansions. Capcom couldn't even do it with USF4, when they'd already done it with SFxT, which is based on the exact same engine.
Actually it has been done several times already on past and next gen consoles - Skull Girls and Killer Instinct appropriately as examples from the top of my head.
Skullgirls is neither previous gen, next gen, current gen or system intensive in any regard, it runs silky smooth on pcs that couldn't even show screenshots of MKX. And both those titles were built from scratch with rollback in mind. KI has the added bonus of being developed for a single release on a single platform. I'll grant that Ki certainly hits the mark for technology impressive and rollbacked, but again day one, before the first line of code was written, rollback plans were already made. The same thing happened with SFxT and Dive Kick. But this is not the same scenario as most of the fighters out there, certainly not MKX which is running on a heavily modified engine not designed for fighters in the first place that's almost 10 years old.
Never heard about any UE3 or even upcoming UE4 based games with ggpo, to my knowledge on how UE is designed in general - it would be extremely hard or in other words extremely time consuming to make it works. On the other hand NRS is a big studio and i can only assume they have like dozen or so programmers, so i guess it's possible if they would commit to this idea. General issue with ggpo or any other rollback system is that it's heavy on cpu, all possibilities need to be calculated, buffered and adjusted on the fly.
I don't know much about UE3 (can't afford a license and never looked into old UE), but I can tell you that Unity, Torque, and many other packages out there are not ready for state based ggpo like technology without a rewrite and thats the divide. Saying "put ggpo in it" is saying "tear your game apart and pray it goes back together for the 1%". No studio is going to take that bet.
That being said in my personal opinion ggpo (or similar rollback system) is the future of any online mode in fighting games.
On that I absolutely agree. I feel all fighters SHOULD adopt this model. However, I similarly feel that the network architects at work at NRS know a little bit more about their engine than kids playing 20 year old fighters on supercade. People think GGPO is just a magic silver bullet. It isn't. Not yet.
However keeping in mind that MK X is in development for like 1,5 year now and they said it's gonna be 1080p @60 fps its safe to assume that the game isn't based around ggpo which is unfortunate. We will have to wait and see what they did with netcode, hopefully its still gonna be a significant improvement over the one in Injustice which was only slighty better then the one in MK9 which in general is considered to be quite bad.
I'm inclined to believe if rollback was happening, it would've been on page one. NRS knows how shit their netcode has been, from Deception all the way to now, they have never done as good a job as their constituents and their community has let them know time and time again about their disappointment. But, they also have to weigh the amount of work it would be with the fact that their games are tremendously successful, even without. NRS isn't just like 10 dudes in a basement making their dream game while mommy and daddy pay for college or on their breaks at a real job. They're people who live and die by their ability to make a quality product in a realistic time frame.
