Oh, you must have that wrong. Security is now the top priority at Redmond. Bill said so.
It is empirical, lets test it.
Observation: browser integrated with OS is a security problem.
Hypothesis: Security is the top priority.
Test: If security is the top priority, MS will seperate IE from its OS. If there is something more important than security about having them integrated, they will not be seperated.
False error analysis: It is possible that there is something more important than security, but that it is still seperated.
All we have to do is wait for the next release! I bet the hypothesis is false.