My opinion is that XP 11 release should be not before 2017. The reason are:
XP11 should be way better than XP10 and use technologies that are mostly unknown today. XP10 with the 64bit support have opened a huge/wide window to the future. Also, a new simulator must be over the top of the existing top hardware. Now, XP10 loaded with addons can kneel down any hardware.
FSX developers and users migration. If Laminar wants to see a tidal wave of users to XP, must stay for some time still, or at least making small steps, to let FSX developers to learn and adapt their work. I'm developing the DC-9 and have in mind what is current to go on. Now if, within the developing phase, a big thing comes in, might give me headaches how to implement this.
Of course I believe that should start making lists with what to implement in XP11.