While I agree that the ecosystem for tablets is more important than for phones, I'm not so sure this will automatically lead to a Windows/Mac situation. Windows benefited a lot from lock-in and network effects. These are becoming less relevant as more services are online. Obviously this is true for web apps, but even native apps usually have a large online component, think Facebook app or Kindle. Because of this, it's much easier to switch to a different platform.
That said, Apple is of course trying to create that lock-in by creating an ecosystem with content (music, movies, etc.) that only works on Apple devices. So you might very well be right that Android tablets won't get any real traction, but I think the forces are less strong than they were for Windows and Mac in the 90s.
That said, Apple is of course trying to create that lock-in by creating an ecosystem with content (music, movies, etc.) that only works on Apple devices. So you might very well be right that Android tablets won't get any real traction, but I think the forces are less strong than they were for Windows and Mac in the 90s.