Warning: contains spoilers for Strange Academy #14!
The events of Scarlet Witch's reality-warping powers, before Wanda undid her own spell and returned the world to normal... or so it seemed. In the newly released Strange Academy #14, it is officially confirmed that the House of M reality does still exist, now wholly separate from Earth-616's reality, which opens up an entire host of possibilities for how the House of M and Marvel's main universe could collide.
The reality of House of M was created after the events of 2005's "Avenger's Disassembled," which saw the Scarlet Witch destroy the hero team following the realization that her two children Billy and Tommy were in fact created by her own powers, so they technically did not exist. This caused Wanda Maximoff to suffer a breakdown, leading to her killing several of her Avengers teammates (namely Ant-Man and Hawkeye) before her brother Quicksilver convinced her to rewrite reality entirely to escape the consequences. Thus came the House of M - a universe where Wanda made the wishes of her nearest and dearest come true, leading to Magneto ruling the world as the head of the House of Magnus, and mutants becoming 50% of the population, oppressing non-mutant humans and viewing them as lesser.
At the end of House of M, Wanda was able to reverse the reality warping spell she had cast and return Earth-616 to its pre-House of M reality. Many of the heroes who faced down Wanda and Magneto what happened, but most have no memories of it at all. Crucially, unlike alternate universes or potential futures like the Age of Apocalypse or Days of Future Past, House of M was set squarely on a transformed Earth-616 and erased at the end of the event. However, in Strange Academy #14 - by Humberto Ramos, Edgar Delgado, and Skottie Young - the students' professor Doctor Voodoo is taking the Freshman Class on a multiversal field trip to the Age of Apocalypse reality. At the end of the issue there is a formal "Time Travel Advisory" for the students of the academy, which confirms that House of M's reality does indeed still exist, and that students should not ask Scarlet Witch about it.
Marvel Comics' time travel, timeline, and multiverse rules are complex and often inconsistent, but the current understanding is that referring to something as an "alternate timeline" is the same as calling it an "alternate reality." Even averted futures tend to persist as their own realities, but as an altered present, it had seemed like fans would never get to see the House of M again. Now that it is confirmed that House of M does still exist as a distinct reality, fans have to wonder what that reality looks like. Did the event itself still take place, with select heroes realizing the truth and ri against Magneto, or is this a world where Wanda's spell stood unchallenged? While many view Magneto ruling the House of Magnus as the main reality-warp that Wanda created, her spell actually made it so that the Avengers and X-Men's greatest desires came true (often in twisted ways), meaning there are a whole host of other stories to be explored in this reality.
There are endless questions raised by the existence of the House of M reality, and that is almost certainly why Strange Academy is keeping the description of this timeline vague. Marvel's alternate realities tend to return periodically, with mainstream heroes visiting them on adventures, or threats breaking through to menace Earth-616, and House of M's world being back on the table opens up some fascinating possibilities, especially for Wanda. Scarlet Witch still hasn't been forgiven for the consequences of House of M, and that's even less likely to happen now that it's been revealed the alternate reality is still out in the multiverse, waiting to become a threat once again.
