That is the key. I doubt Apple is just going to release a laptop replacement. Whatever it is, I imagine it is going to integrate with the rest of the Apple digital lifestyle in some way and that is what will make it sell. That is where the other slates/tablets fail. They are just laptop replacements so the use of them is confusing to the market.
Agreed, what few if any analysts are doing right now is trying to parse out what products are part of a convergence in Apple's future development. The focus tends to be on the product itself - not where Apple is taking the consumer. But that is precisely what Apple is doing - first with the Mac, then the iPod, the iPhone and now - whatever it is that is next in line.
You see the same sort of convergence being discussed by Microsoft house devs as well. Except, Microsoft tends to focus first on marketshare and proprietary ownership, which may be their Achilles heel in all of this. The personal computing market is effectively saturated in the US. This is the primary reason why Microsoft is bleeding marketshare. Once saturation hits, the market driver is differentiation.
This is also why Dell and HP and Acer and everyone else making hardware were so successful earlier and now you see their market segments flattening out too. This is why netbooks were able to become popular - differentiation. The problem was that they are inexpensive and therefore a very low profitability. It is possible to look around the consumer marketplace and watch for telltails of where consumer interest is going to be, but a good company will drive market interest with compelling products. Apple has demonstrated they can do that with their previous products.