Ok take this anecdotal evidence with a grain of salt but I was hanging with a NYC MS exec last night (he was in a private meeting with Balmer today) and he basically told me that Elop is looking out for MS interests (he is not a trojan horse per se) but they will not buy Nokia. The deal they signed has Nokia locked in for years with WP7 as their 'primary smartphone' platform and they will give Nokia engineering and marketing support.
MS want Nokia to be successful so the stock price drop has been quite a shock to the company they were not expecting it. Essentially the deal is structured as such that literally there is no need to buy them.
He also dished on Skype which is going to be integrated into every MS product. They are working on integrating it into Lync, Live messenger and Xbox live.