He didn't say exactly how many apps are to flood the Windows Phone Marketplace, only that there are "lots of apps" coming for us. Even more interesting is that he points out that the apps he has seen are "completely new", which promises a lot and this is hopefully only a sign of things to come.
Just to remind you that the Windows Phone Marketplace has already passed the 1400 apps mark and that 12 000 developers are writing applications for the new OS platform. All this means that when it comes to the number of developers working on apps for Windows Phone 7, it is set to be leader in 2011.
source: WP Central