Who knows?   The Boston Globe speculates, though: 

The idea of a Warren Senate run is not new, especially to Globe readers. Last year, Ethan Porter wrote an op-ed for the Globe (and a blog post, earlier, for the site True/Slant) explaining why Democrats desperately need Warren to run for office. Just days after Brown’s surprising win, Porter wrote that Brown’s victory “made clear that voters crave something besides the norm: someone from outside the traditional political structure who can speak to their everyday, bread-and-butter concerns in a credible way. Warren fits the bill.”