But what MS and Google both know is that the drive is upwards from smaller devices to larger. People running networks of Windows will look first to MS to fill their needs when they grow into larger systems. This is why the smartphone/netbook OS is important: if Google Chrome or whatever looks like it can do a convincing job of running on PCs as well them it's a foothold into that market
These things go upwards not downwards. You only need to look at the all-conquering Windows Mobile to see that