Whether she appears in Vegas or not, the singer plans to keep touring and recently auditioned for dancers in London to appear in a proposed tour next autumn.
A source said: "It's going to be her biggest, most unexpected tour to date. She is going back to her New York City roots, with a street/hip-hop feel, and wants to make it a physical, dance-heavy set of gigs."
The as-yet unnamed tour - which is part of Madonna's deal with Live Nation - is expected to net the singer in excess of £100 million.
The singer's last world tour - 'Sticky and Sweet' - finished last September and grossed an estimated $400 million in ticket sales.