I don't live in the UK, but I must admit when I saw the DNX408 I first saw something in 1/8th scale buggies. When the DEX408 came out I thought 'I gotta get me one of these!'
But... The RC world is pretty small here in the Netherlands. So there's probably almost no-one driving 1/8th electric, at least not enough to make a proper racing class. With that problem, it's simple, I don't buy one, because I'm not going to bash with a car like that!
Plus, I'm now settled in the 1/10 scene, and I don't have the resources to drive a two classes (doing seperate events).
Anyway, to answer your question... I think Nitro is there to stay for a while longer... There are hardcore petrolheads out there that won't stop driving nitro. However, I think slowly but surely the 1/8th class will grow. Eventually probably with a big turning point where they'll suddenly become very popular.