In Feige I trust.
There are an infinite number of ways they can do the FF, but based on what Marvel has done with their other characters, I trust that they will look at the gestalt and do something that captures the key elements that have defined the FF over the past nearly 60 years.
Unlike Fox, I think Marvel recognizes they can't just take one goofy element out of one story line and say: "It's 'comic accurate'. We saw in issue XXX that Reed was transformed to a ferret, so the fans can't complain if he's a ferret in this film."
I would prefer a modern FF because, as others have pointed out, they've always been on the cutting edge. But if they decide to do retro, I can see the fun in using Kirby's panels as story-boards with Johnny playing around with real old-time hot-rods, Reed smoking a pipe and wearing a coat and hat, and the retro futuristic Kirby designs with big, bulky cathode ray tube computers and big, bulky tubes, hoses etc. that seemed futuristic in the '60s but would look kind of clunky now.
But at this point I'm willing to sit back and see what they do. Every time a new Marvel film has come out, I've had mixed feelings. I've been thrilled they keep managing, over and over again, to find ways to bring these characters to life so masterfully, but I've been frustrated that they haven't had the chance to work their magic with the one property that I REALLY want to see.
So I'm just looking forward to whatever they come up with.
... and I'm not counting my chickens yet. I've felt this way for the past 8 years as I've hoped and hoped. Now it feels like it might really happen, but I've been disappointed too many times to celebrate prematurely.