Google themselves said that even the latest version of Android, Froyo, is not quite ready for tablet use. The UI is just not designed with a tablet in mind. Hopefully, this will change with the UI overhaul of Gingerbread, but until then most manufacturers will have to accommodate Android for tablets. To do that they need to change the UI a little bit.
But this is not even the only big problem Android has right now when it comes to tablets. Another big problem is that because Google doesn't consider any of the previous versions of Android ready for tablets, whether it's because of the UI or the low standard resolutions, they won't allow access to the Android Market for all these upcoming and previous Android tablets. As a result, a lot of manufacturers are starting to create their own app stores and get developers to write apps for them.
If Google wants to really take over the tablet market and catch up to Apple, they need to allow access to market for tablet apps ASAP, and they need to also make an UI that's more natural and intuitive for a tablet. If all these don't come with Gingerbread, it will be quite a disappointment because that means Android tablets won't be truly competitive with iPad until next summer when first Honeycomb tablets should show up. That's a huge window for iPad and it will continue to dominate the tablet market.