well I suppose it's all down to what people look into a flight sim.
Does the DCS Mustang look promising? Hell yeah! Will it actually be the beginning of a serious competition? It's too early to say.
It will be down to the level of detail of the plane, the quality of the flight model and damage model, the overall feel of realism it gives you once you're inside..
It's a bit risky to develop such a project and leave it without something to shoot at, I suppose they'll use it as a benchmark and decide what to do from there.
As for the landscape, if we could combine the level of detail of CloD with the colour palette of DCS stuff, we wouldn't have to go out anymore!