i dont think so - some stores have an idea of how much stock they will be getting of the initial 4 million units - in fact i doubt they know how many europe will get until the release in a few weeks in the US.
xbox 360 is well on its way to selling 10 million units and the ps3 shortage stories have been on the net for some time and nintendo may have a problem as well - while the wii is easier to make and they ahve made loads of them it seems its very popular
personally im waiting to see what amazon.co.uk say and if they can promise launch day (they are one of the few major retailers to not offer pre-order yet simply because they dont know how many they get) i will buy from them - if nto i take my chances in the high street