Just curious, but who do you think has the best chance of at least being a competitor?
I would have to guess that Android has the best chance. I believe they have the second most mature app store in the market. Like you said, Android is a mess right now. On one hand its great that any manufacturer can design a tablet and throw Android on it. At the same time, that very benefit is causing a lot of Androids problems. I know that Android is working on a resolution independence thing, but I have no faith in that. Look at the lengths Apple goes to in order to control screen resolution. It's either you double the resolution, or you don't change it. That makes scaling apps work perfectly.
Android also suffers from a branding problem. No one thinks a Samsung tablet is "sexy" or "nice." Acer doesn't make Joe Consumer think of quality. Apple has a tremendous advantage here, where people already assume it's infinitely better just because it's Apple. (And, well, it is!)
Microsoft may have a chance too. Who knows though. The Zune "looked" neat, but damn that was a failure. Microsoft could do some really neat stuff if they integrated connectivity for XBox Live, etc. But at the same time, Microsoft just can never seem to appeal to anything slightly artistic.
For a company that doesn't have a tablet, my money would be on Amazon. They already have an insanely huge infrastructure. Almost everyone already has an account on Amazon. They have music, movies, and an app store. However, Amazon really screws developers on the "Free of the day" thing, so I don't know if devs are withdrawing from Amazon's app store, etc. Also, Amazon has experience producing a successful device.
Who knows man. I don't see anything on the immediate horizon.
We all like to say that we want to see competition, etc, to stimulate Apple to innovate. But it just seems impossible for any company to compete with prices, quality, eco-system. Who knows. The good thing is that Apple doesn't necessarily need competition. People will keep buying iPads and upgrading year after year. I'll def sell mine and upgrade if a double resolution version comes out next year.
Sorry that this is all ramblings. I'm three beers in.