Since Samsung started putting the "Galaxy S" name on just about any phone from mid-end to high-end, and because even Samsung's Galaxy S "flagships" have never really had a very "premium" feel about them, it seems Samsung wants to launch another flagship series, that's more premium, and will be called the "Galaxy F".
Whether this means that Samsung will keep the Galaxy S at the "high-end", and make Galaxy F a "super high-end" phone or not, that's unclear, but I think that would be a mistake, because it doesn't seem like it will have specs that are much better than what a high-end Galaxy S5 would have. It's rumored to have a Cortex A57/Cortex A53 octa-core processor (64-bit ARMv8 architecture), and that's also been the rumor for the Galaxy F so far, along with a flexible YOUM display.
If they do use that flexible display, hopefully it's not for a very gimmicky design, and they will mainly just tout how "unbreakable" the display is. I think that would be a lot more important for people to know than seeing some curved edges, or whatever Samsung can come up with in terms of design, which actually worries, because their old design team is not very good.
That brings me to my next point. I do hope Samsung has hired better designers, because it started being obvious since the Galaxy S3 that Samsung's designers aren't great. The Galaxy S was mostly done after the iPhone 3GS, and the S2 seemed like the only one that wasn't awful to me, but nowhere close to having an "iconic design", like other OEM's have managed to with their devices.
If the Galaxy F is really meant to be a "premium" device, with a metal chassis, then I hope they will use great designers for it, too, to give it a very nice design. Design and finish is extremely important when it comes to evaluating how premium or how high-end a device is, and Samsung needs to spare no expense in that regard, nor can they afford to become complacent with their design team, and just accept whatever they are giving them.
The Galaxy F is also rumored to come with a 16 MP camera, which might start to become overkill in terms of processing power, and how much harder it has to work to be good in low-light, although it will have OIS, which has become a "must-have" for all high-end smartphones. The device is supposed to come out early next year.