According the data from Gartner, 43.3% of the smartphone hardware market is controlled by the "others". The "others" do not include LG, Huawei or Lenovo. 43.3% is larger than, the combined share of Samsung and Apple that is 24.7% and 15.4%, respectfully. I think that Microsoft might be able to expand if it researches the operations of this segment.
As for the software part, Windows only has 2.8% of the market share. It will be interesting to see if Windows 10 manages to change the equation.