So I'll try my hand at estimating XB1 WW LTD based on previously released numbers thus will rely on some terrible assumptions I'm afraid
Xbox One: over 3 million sold to consumers in 2013
XB1 US LTD in 2013 = 909,132 [Nov. NPD] + 908,000 [Dec. NPD] = 1,817,132 units sold
1817/3000 = 0.6057 -> XB1 US sales for 2013 accounted for 60.57% of its WW sales
Thus with the new XB1 US LTD = 2,527,132
2527*(1/.6057) = 4172.26 ->
Thus XB1 US LTD suggests XB1 WW LTD of 4,172,260
*Note I strongly feel that the XB1 sold better at launch in the rest of the world than it is currently doing since the last official WW sell-through number was given hence it is likely more than 60.57% of XB1 WW LTD sales are in the US
For instance if that number was now 65% [Less than 4% more than launch ratios], XB1 WW LTD would be 2527*(1/.65) = 3887.69 -> XB1 WW LTD of 3,887,690
I seriously think there's a decent chance XB1 WW LTD could be under 4M right now which is crazy