I would bet everything that not one of those devices sells 2 million in the first two months like the iPad has, probably not all of them combined will even come close. Sure, they're all marginal competitors, but when they are running a full OS like Windows 7 they are destined to fail through poor user experience and sluggish performance. People want a tablet device to be simple to use and quick at the tasks it is required to do.
The android tablets do look a bit more hopeful as they, like the iPad, run a mobile OS, but I don't think the Android OS is quite there yet; I'm not saying it wont ever be, but it isn't yet.
I still find it kind of funny that the whole industry is permanently playing catchup with Apple by releasing 'me too' products that are rushed out the door in a couple of months with more problems than features; there is a reason it took Apple 3 years to bring us the iPad.