Seems like they're preparing a new part of Time Temple.

Source?
Because what it seems like is that the door is open, and you can get in, but when you get in, it's a possible future that this guy made and is showing you, mainly to scare the living bejeezus out of you and demoralize you (incidentally, also making you stronger).
This future still could happen, you must realize. It's one of many possible futures.

I posted the full text earlier in this thread.
I pulled the quote directly from Quest.wz (of the recent Tespia client, not that that matters).

But, yeah, that's exactly what the dream is meant to be: a discouragement.

It could theoretically occur, but there are a lot of "maybes" in the way.
Namely, Cygnus would have to actually be obsessed with finding the World Tree and empowering the Cygnus Knights so that they could take the glory.
However, the very fact that Cygnus has allied with the Adventurer instructors would indicate that she's swallowed her pride and is willing to let others shine as long as it's for the good of Maple.

Personally, I am doubtful that the Gate to the Future will ever truly be opened. I do expect that we'll see more altered futures (and, likely, altered pasts).