Hmmm will it be first or third person though?

And 80% underground? That's boring. make it a nice even split else it'll get as dull as guerrilla with always the same overhead.

Also adding an orbital space station to the mix would be nice so that you could go up there as well.

Hmm 80% of it under ground. Why. If this is a sequel why under ground? We spent almost entire Red Faction 1 Underground because the air was not survival. And what could we destroy. Isnt like there are citys under Mars. I like Geo Mod 1.0 But i like to destroy buildings. In Geo Mod 2.0. Maybe we get Geo Mod 3.0 Destory Ground and Buildings ( Doubt it.) Would we still play as Alec Mason. Need some strong character for the series.

I wont believe it unless it comes from a Reliable source. 

I don't know, in one hand it will bring more chances for a deep narrative, in the other I don't think RFG2 should loose its sandbox and 3rd person roots.

Will wait with interest to know more details.

Actually Red Faction's roots are in linear, FPS games. The first game was practically Total Recall on a Half-Life 1 engine, only RF was prettier, had destruction, substantially less Arnold Schwarzenegger and science (sadface) but substantially more fun and creative weapons (happyface), hammy characters like you wouldn't believe (JUST YOU AND ME, MINER!) and was, in my opinion, having played both, more fun.

As for RF4, I'm quite hopeful for it. They said it'll be "structured" - think of it this way. Compare to Assassin's Creed: The first game was straight-up open world, with a loose story to guide you from one arena to the next, much like RFG. It was awesome, for a while, until repetetiveness set in and became bland and boring. Finishing the game was more of a chore for me than anything else. Compare and contrast with Assassin's Creed 2: This game is more structured and linear, but still open-world; you're free to go wherever you like, but the intended gameplay direction has a set path through the open world, driven by a fluid narrative - rather than "Go to a city, gather information, kill some fucker" it's "Go to your next objective and see what you have to do" - there are even similar information gathering missions, like beat up events, eavesdropping, etc. but they're tied together in a linear way with a story, that makes more sense and makes it more interesting. THIS is what I think RF4 is going for; instead of being dumped in a sector with 3 story missions to complete in any order, and like, 15 side objectives, you do the story missions in a prescribed order, and the side missions are just that - side missions, that you don't have to do if you don't want to, although it is advantageous to do them (eg. in AC1 you HAD to do at least 2 side missions to continue to the assassination. In RFG you HAD to do enough side missions to lower EDF control to zero, or you could plan your own assaults on EDF strongholds, which was infinitely more fun. However, in AC2, you don't need to touch the side missions, but you get money for doing them. So, in RF4, they could have side missions that you don't have to do, but they give you salvage/mars dollars/funny money when you do).

As for it being 80% underground, this could be anywhere and for any reason - they said it takes Red Faction to a whole new place. What could it be? Another part of Mars where the surface is irradiated? Another planet? Who knows? It's wide open.

All in all, I'm still wetting my pants over this game.