I'm neither a fan or hater of Xtina, but am always interested in the machinations of the music industry, and it seems to me that the label has just lost interest in her. It's hard to say why - maybe it was the insistence on working with Ladytron, Sia etc., maybe their focus groups said that the married-with-baby lifestyle alienated her core audience, maybe she refused to perform at the MD's birthday party... whatever it was, she was no longer a AAA priority artist.
The cost of recording an album is nothing compared to the cost of marketing one, and the overriding impression I get is that the label just decided to put "Bionic" out with minimal spend, see what the fans thought, and maybe add more spend later... but when it didn't catch fire, they dropped it completely, and I'm going to take a wild guess that this was the point at which the label decided to withdraw tour support, hence the cancellation... right now, they're doing the bare minimum to show they're still pushing the record (releasing singles, making videos), but I doubt they'll be paying her huge sums to support TV appearances...
She's not done as an artist by any means - she easily has the best pipes of any singer out there (if she'd just quit the melisma nonsense and avoid the sappy ballads) and probably just needs to take a long break out of the public eye and come back with a great adult album...
PS personally, "Burlesque" looks to me like some unholy cross between "Showgirls", "Striptease" and "Glitter", but you never know what might happen!