well, it takes money, ideas, and execution.
I know MS has money and lots of it.
I'm pretty sure they have ideas, or all the 'talk' would not be surfacing about "THE GREAT SEARCH ENGINE".
Now, when and if they can execute is another question.
I'm guessing sooner or later, MS will come out with a search engine... whether or not it will be better than Google or Yahoo... have to wait and see.