I wouldn't necessarily count on them being that close to anything that amazing at least from a technical standpoint. I'm starting to realize that as a company gets big, it takes more and more people just to keep things going, make sure their systems don't melt down, do support, analyze all the useage data they're generating, manage the other people, etc. They're only at like 60 employees, right? That's really not many for a site with 25M users, many of whom run an agent that constantly hits their servers asking if there are updates.

Twitter's done a lot of hiring (up to ~500 people) and not a lot of releasing (last real release was ... new twitter?). Are they working on something huge and secret? No, they're keeping the site from melting down, making things more efficient so that that they site won't melt down in a few months, and making incremental improvements to the growing number of pieces of their service.

I'm sure Dropbox is working on more, but I don't think that they've made significant progress on anything earth-shattering. I'd guess that they're showing investors some very solid revenue and usage trajectories and some plans on how they're going to extract more money out of more companies in fairly obvious ways. Maybe some early prototypes of something earth-shattering.

(Cue giant release proving me totally wrong within a month)