They showed the Tegra 5 running BF3. Not bad. Now imagine the future in which Mantle actually gains traction. Desktop Space prefers AMD cards (short term) due to mantle advantage. Furthermore, developers make a push into the mobile phone gaming scene since the graphics horsepower is there for 3D games with the likes of Tegra 5 and AMD's SOC with GCN Graphics. Gamers decide "Hey, I can play BF3 on the go, that's cool" and pick up a tablet with AMD in it.
Currently would I touch AMD with someone elses money on mobile? No, I'm not that cruel. But I do see the potential for an AMD GCN enabled tablet in 2015 if Mantle pans out.
I don't know the details of AMD's console bid, nor will I try to speculate like most people but that's their ONLY surefire cash. Graphics, for some reason no matter how well they do, they can't make the same margin Nvidia does, Desktop CPU wise is really dependent on how well mantle works to close the gap between intel and AMD, and mobile really it'd take magic for them to catch up.
They have a chance, but meh there are a lot of movements they are making and one mistake and it all crumbles.