
We've talked to Coleman once before about IMAP and Greasemonkey back when Google started rolling out some serious changes, but since then the email application has been progressing at lightning speed. Here's what Coleman had to say about five years of Gmail, and what we can expect in the next five year.
Lifehacker: After five years, the most obvious question to ask off the bat: Can we ever expect Gmail to leave beta?

Lifehacker: When Gmail launched five years ago, did you guys have any idea you had something quite so game-changing? (Archiving vs. Deleting and threaded conversations were new, but they also changed everything people had been trained to expect from webmail. Incidentally, I can remember paying $5 on eBay at the time to get an invite.)
Coleman: The goal was really to build an email product that worked better for people, and the team had a willingness to rethink the experience from scratch. Of course there were some significant user expectations to account for (based on the past 30 years of email usage and products) and some basic constraints accepted (e.g. SMTP) but a lot was up for rethinking. That included the architecture—a combination of HTML and JavaScript that became known as AJAX—as well as some of the user experience changes you mention, like conversation view, search, labels and the freedom of not having to worry about storage space. Like most Google products, Gmail is designed to work for the most demanding users, and its first users were Googlers who really pushed (and today, still push) it to its limits. It's always hard to predict whether any specific product or feature will take off, but our approach of everyday-usage-by-demanding-internal-users (which we call "eating our own dogfood") helps us build things that we're confident are at least useful. With Gmail, it's been great to see that many other people found these changes useful, too. And the changes are never done. The demands we're seeing from our most active users today are leading to some big rethinking.
Lifehacker: Right now some of the best/coolest Gmail functionality is coming from Google Labs. What's the future of Gmail Labs? Will Labs ever open up to non-Googlers?

The Labs architecture allows changes to literally every part of the Gmail code stack—from the storage server to the JavaScript—and requires compile-time integration, so it wouldn't be the right technical approach for non-Googler development. But we are interested in expanding the number of people who can contribute to this experimentation. In fact, one of the Labs, "Add any gadget by URL," is a small experiment with this. We also have a small, experimental Greasemonkey API.
Lifehacker: In the past five years, what are the coolest ideas you've considered but not implemented? Why not?
Coleman: We are working on some of the coolest ones right now. I am pretty sure we're not going to finish Autopilot anytime soon, though.
Lifehacker: A lot of people would kill for a desktop version of Gmail. Is Offline Gmail the best they can expect, and if so, what plans do you have for Offline Gmail in the future?

Lifehacker: I know that in the past Googlers have been the initial guinea pigs for new Gmail features. Are there currently any major differences between the Gmail you use inside Google and the Gmail we use every day?
Coleman: Yes, and we are very excited about them. They involve some non-trivial changes and need more work before they're Labs-ready.
Lifehacker: Gmail seems to have been progressing in leaps and bounds in the past year from the users' perspective—especially compared to the relatively slow development we were seeing to the front end in previous years. Can we expect more exciting developments? Integration with Google Voice? Etc? What do we have to look forward to from Gmail in the next five years?
Coleman: Stay tuned for more, and keep the feedback coming—the team really values all the responses we get on Labs and other launches. As for what's next, we have a lot of ideas and many ongoing projects, though we like to avoid pre-announcing anything. This is in part because it spoils the surprise, an in part because we wouldn't actually know what to pre-announce. Our products evolve in big, unpredictable ways as we develop them internally, and most of our predictions of what would launch, or when, would be pretty inaccurate. That said, we are working on some exciting things and pay close attention to user requests—we read a lot of comments, especially on sites like Lifehacker where some of our most demanding users post their ideas.