Although I can see how MAYBE not all the quests will still be there after Halloween, it would seem most will be, along with the monsters. They drop regular equips along with the Halloween items.
This whole thought process that people are so angry about this, and will be even more angry if they don't get the whole deal after the event is ludicrous to me. I'll never grasp the concept of feeling OWED or ENTITLED everything and anything by a company providing me a product I do not pay for. (Now, providing service and products for what I have paid for, different story.)
All that said, the maps are really nothing to get worked up over. There are so many doors and it takes awhile to even get a feel for how to get to places. Spawn is very very fast, but mobbing is impossible as the number of monsters in locales is low or very spread out. There are quite a few rooms that are very small (nearly just what you can see on your screen) and only spawn 4-5 monsters at any given time. The quests are nothing fantastic and give you nothing fantastic.
So, in conclusion, I love this idea and would like to see every new area released this same way. NX only for a few weeks, and then open to everyone. For those who choose to pay, they get a few weeks to explore without it being insanely overrun, for those who choose to wait, they get everything, or nearly everything, for free, but have to wait a bit. I really don't feel there is any argument against this other than the inept 'Anything and everything in the game should be free and equal at all times to anyone' which would also rule out cash shop completely, making a company unfunded and unable to provide most of the game free to the public.