It would be a marketing diaster to release a new OS only after 2 years. The loss of sales on Vista would keep it from recouping expenditures of its development. Although to contridict myself, Windows 2000 and XP had a 3 year span between them. So 2010 is still the earliest we would see a new OS.

Now if those pixs are valid then it would appear that they are building it off of a Vista base so less work needed as its not being developed fromscratch. This could be because of all the dramatic changes they implemented with Vista in preparation for the next OS.