(This post is written on my personal assumptions and I premise that I did not personally try the Developer Preview of OS X Lion)
Rumors reported that Apple already finished developing the new version of iWork apps: Pages, Number and Keynote. It was also rumored that Apple would release the new suite alongside the Mac App Store. I bet Apple will silently release the long awaited new version of the productivity suite alongside the release of Lion, instead.
I presume that the new versions of iWork ‘11 is so much depending on Lion’s new technologies that they might not make a version available for Snow Leopard. This is just my theory though.
One thing for sure is that Apple is finally making tons of money on software, with iLife and iWork apps nearly-constantly in the Top Grossing ranks of the Mac App Store. This is happening because it’s much easier for the average users to find out about these three apps. Instead of pirating them – that is what most technical users do since it’s really simple in this case – they just buy them, also because they are rather cheap after all.
So why Apple should not keep riding the wave of profits and wait for a good shift and sell a new version of the app? It’s just a marketing decision to postpone an awesome, finished product.