Aside from market share gains in NA and UK, I also feel they will make headway in South America as well. For some reason I read in another topic that Xbox games cost less then PS games in certain countries there.
In the Analysis, I assumed they will make gains everywhere, although proportional to their current market share, so the gains in South America is relatively smaller and lumped under the "World Other" category. This estimates that the "World Other" market share for Xbox will increase from the current 24.4% to 25-27%. I tried to depict all this with two nice tables but for some reason the blog would not let me integrate it properly.
Here are the two graphs as regular links:
1) PS4 vs XB1 Analysis
Regional Analysis (only MS and Sony Consoles)
Europe => XB1 : 23-24 % vs PS4 : 76-77%
N. America => XB1 : 49-52% vs PS4 : 48-51%
Global => XB1 : 32-34% vs PS4 : 66-68%