While teased last week in Powers of X #1, today's House of X #2 fully reveals what that scene entails and in doing so, completely rewrites the entire history of the X-Men.
[Spoiler (click to open)]Moira MacTaggert is not a human as we were always lead to believe, but a mutant with the power of reincarnation and the ability to prevent mutants from discovering her power. She has spend 9 lives trying to change mutant lives for the better with poor results. In life 10, she meets with Xavier and makes him read her mind as seen above, leading to everything that has happened in the comics since. The timeline of her lives at the end of the issues also confirms that she is currently still alive, and was not actually killed off back in 2001.
The relaunch continues with Powers of X #2 next week.