I'm actually pleased by this news. If this has been mentioned 12 months ago, absolutely not, but right now I think this is a really sensible move given her current career status. Vegas is a very structured environment - it'll get Mariah much more into the performance mindset without the pressures of conventional touring. A bit like rehab for singers, she can lock herself away in Vegas and really brush up her craft without battling every countries excessive media drama (I mean, who gets extreme media scrutiny from Vegas shows? Even with Britney, no one gives a sh!t what is going on night to night).
Perfect place to stop over for a while, plus some time to reflect on her next move and the best way forward.