We were there in April. The staff checked our room keys before they took us to the special elevator.
Thanks guys. I guess we will settle for a few drinks at the Poly lounge. I'm certain BLT will change their policy about the lounge soon after it's all sold out.
Let me just say that is possible to get up there without taking the "Special Elevator" and without staying at BLT
Is it for DVC members and their guests (who would not be owners but are staying in the room with the members?)
Due to anticipated high demand for this location, access is available only to Disney Vacation Club Members who are staying at Bay Lake Tower using their Membership (Vacation Points or cash), guests staying in the room with that Member, and guests who are staying in a room reserved by a DVC Member with Vacation Points. Access is limited and available on a first-come, first-served basis.
If I'm there with my family, do we each have to show our room key?
Depends on the CM working the desk. Some ask to see a KTTW card for everyone and sometimes they just want to see one. I have had it happen both ways.

Let me just say that is possible to get up there without taking the "Special Elevator" and without staying at BLT
How? Love it up there.Like take it away completely.

We were there last July and they turned DVC members away who were not staying at BLT. They claimed they owned at BLT but were staying at another DVC that trip but they still got turned away.
Personally, I hope it does not change. It is a great lounge and not overcrowded so I think by keeping it to BLT guests it makes it a lot more comfortable. We have always been able to find a table and relax after a long day.