What indication did you have that iOS was ready for a tablet? As far as I can see, it was barely changed at all for those purposes, but it works ok.

There are rumors that Gingerbread (Android OS 3.0) will have some stuff in it for tablets in addition to making the OS generally nicer looking.

Android in and of its self may not be marketable, but a less expensive alternative to an iPad will always be marketable, and clearly there's something to the OS given how many phones have been shipping.