The website where you do your online booking now states, at least for Beach Club and Boardwalk, that a one bedroom will sleep 4, but allows 5 adults if you provide your own bedding.
Maybe this will help. My husband and I have 3 adult children, unmarried, who live in 3 different cities. One of them is a Disney employee, working at Walt Disney World right now! Anyway, over the years, we have done different scenarios, from for example, reserving a 2 bedroom, only to have 2 of them come, hence too much space, to reserving a 1 bedroom and having our daughter who has her own apartment, stay with us, making 5 in the one bedroom! (She has 4 roommates, so she likes to move out for a bit!)
Bottom line, it depends on your family. We can share a bedroom, and we see each other so seldom that the closer quarters are fine. Our daughter usually puts a blow up mattress somewhere. The men in my family are 6' and taller if that helps. Bay Lake Tower with the 2nd bath makes that a better choice when possible. And of course 2 bedrooms is better, but I only have 200 points, so I like to budget them!
That said, this past Christmas, the five of us were in a one bedroom at Beach Club Villas. My brother and his family were staying at Port Orleans, and my cousin and her husband drove up from Palm Beach County for the day and we had a nice Christmas Dinner and celebration in our room, with some walks around the lake for atmosphere. It was lovely, lots of good memories!