I use a similar argument to illustrate why there will probably always be separate gadgets, such as digital cameras and digital music players, despite the potential to integrate everything into one device (generally centred around a mobile phone). Most of the arguments which justify hi-fi separates will carry through to the gadget world - smoother upgrade paths, less chance of crippling failure, greater robustness etc. (the old, "small pieces, loosely joined" mentality). Of course, the downsides will apply too - separate components make for bulkier systems (more to carry), and the price is inevitably higher.
All this talk of convergence reminds me - I really want one of those Swiss Army Knife USB Storage things.