I think it will a harder convince than, for example, HD. Esp with the glasses (and the Active type being expensive).
And even with the fact most aren't keen on the idea yet (and the demos and regular programmes are OTT with the effect), most people in a position to spend £1000 on a new TV have likely bought a new, large panel TV in the last 3 years. Assuming they weren't daft enough to go plasma, its likely it they will last a fair bit longer yet.
3D won't be enough to make most people upgrade TVs. And I know more people dropping Sky (the only place to get 3D) than taking it on. Those that are taking it on are doing so purely for sport, and current 3D sport broadcasts are unwatchable (due to the desire to over emphasise), and who wants to sit for hours with the stupid glasses on?