I see that slightly differently. Oracle is huge in government, world-wide. But while it used to be "Oracle is the answer. What was the question again?", there's a shift towards F/OSS, open standards, and commodity hardware. This hurts Oracle. And yes, the exact same thing hurts Microsoft, too.
Microsoft, however, have three products that will ensure their continued profitability[1] - Excel, Exchange and (probably most importantly), Active Directory. This is over and above their insanely cohesive ecosystem, from SCCM all the way to Dynamics.
Active Directory is so critical because of the vast amount of legacy code that depends on it. Want to guess how many fortune 500 companies rely on AD?
[1] Nothing is guaranteed so yes, unless they evolve as the environment they generate value for inevitably evolves, they'll go.