iPad 3 launched 3/7/12.
Surface announced 6/18/12 ... over 3 months later.
Surface is expected to launch 3-6 months after announcement ... 1/2 to 3/4 year after iPad 3.
iPad 4, presuming Apple's growing-typical annual cycle, will launch March 2013.
Now consider that the primary selling point for the still-vaporware Surface is not memory, speed, capacity, resolution, or even it's much-vaunted cover/keyboard. On specs alone, Surface is either behind the curve (to wit: iPad 3) or only marginally ahead of it. Assuming delays, it will arrive just 3 months before iPad 4, and at a price which many assume will give buyers pause (if not prevention) to purchase. Assuming one-year product cycles for both, that leaves Surface behind - perhaps way behind - iPad 4 for 9 months. Is the sole selling point of Surface - the ability to run Windows (and for half the variations a stunted version thereof) - going to be enough?
Oh, for sure, it'll be enough to sell ONE GENERATION. There are tons of people salivating all over themselves (and apparently spewing other bodily fluids as well) at the thought of a REAL MICROSOFT TABLET WITH WINDOWS. Hell, I find it an attractive thought myself, given the amount of time I spend with Windows every day.
But I believe the Moment of Truth is not the opening day of the first generation Surface. It's whether Windows on a tablet actually works, and makes people happy and productive. In other words, how well will the SECOND generation Surface do?
Microsoft is even admitting they're not so sure about that prospect, since they're implying strongly that they'll leave the second generation to their OEMs. They're hedging their bet.