While I can't speak for someone else, I find myself in the same place: I have 16GB in my mid 2010 MacBook and it's not enough when you develop with Xcode (incrementally eats memory up to and over 1GB), have an IntelliJ (~1.5GB) up while having one or two ubuntu VMs running (each 4 GB). Add to that the fact that Chrome eats a terrible amount of memory and all these developer tools running at the same time (kaleidoscope, sourcetree, db browser, xemacs, sublimetext, etc) have their demands as well, and I find myself running out of memory all the time. Fast paging doesn't do the trick.

I don't need it now, but I like it when my equipment lasts as long as possible. I've seen other manufacturers creating laptops with 32 GB RAM, so I know that it can be done.

If I'm going to buy a state of the art computer, I want it to have state of the art specs, know what I'm saying? I think it's inevitable that 32 GB RAM on a MacBook will be a thing, so that's what I'm waiting for.