Some may say that Windows 7 is a tablet OS. I think Windows 7 is a nice OS for tablet PC users who are using a Wacom or Penabled stylus pen. It's difficult to compare Windows 7 against iOS, webOS, or Android if you're mainly using finger touch for primary navigation. That's probably why Microsoft is going to release a tablet OS in 2012. I think that many people are concluding that Windows 7 is not an optimal OS for touch-screen slate tablet PCs. My prediction is that the Microsoft tablet OS will look very similar to HP (formerly Palm) webOS. Some are already saying that RIM's BlackBerry PlayBook is using an OS (BlackBerry Tablet OS) that closely mimics HP webOS. I won't get into that right now.
Eventually, will these tablet operating systems become so powerful that they essentially replace standard desktop and laptop operating systems? Perhaps this may happen as cloud-based computing evolves. After all, if we can compute off the cloud, then who needs a robust OS? You just need a robust (and fast) connection to the Internet. Let the cloud provide all the software services that you need.