When your city is booming, the question of its future tends to be approached with a little dread, because booms always end, sometimes badly. But the speakers at our Future of Downtown Seattle event recently were optimistic about the future. The boom will end, but not for a while, and it might be a soft landing when it does.

Sightline Institute founder Alan Durning gave the opening remarks. He said metro Seattle has had a phenomenal record as a generator of new ideas and new approaches, with a long tradition of innovation in both the public and private sectors, and those two working together. Though not particularly large as a global city, Seattle punches well above its weight. In terms of global-spanning brands, Seattle's a big deal.

Seattle's experiencing a great boom, adding 40 people a day to just the city, and with a growing economy that's the envy of the world. More than half of apartment construction in the region is happening in the city—which is fundamentally different than other periods of growth. It's smart growth, driven by economics, demographics and policy, because one of the defining aspects of the Seattle brand is its commitment to environmental conservation. Figuring out how to do things a little greener is an essential part of the city.

The Seattle boom was on our speakers' minds, and when talking about the boom at this stage of the game, the question naturally arises: Can it last much longer? The consensus was probably so. First some facts: 65 major buildings are under way in Seattle, two-thirds of which are residential. A third of the office space under construction here already has been taken by Amazon.

The area's job growth fuels demand both in office and residential, and as long as that goes on, space will be absorbed. Amazon's cloud division by itself promises to drive as much job growth in the coming years as Amazon's marketplace has in the last few years.

There might be some brakes on new development over the longer run, the speakers said. The costs of land and construction are quite high, and lenders are little leery, or at least more selective, about the projects they fund. So development might slow down.

Bentall Kennedy SVP Steve Reents, Continental Properties president Claudio Guincher, Clise Properties president Richard Stevenson, Downtown Seattle Association CEO Jon Scholes, and Cairncross & Hempelmann attorney Matt Hanna, who moderated.

One major challenge: It's almost impossible to develop affordable housing in Seattle, certainly without subsidies. A partial solution to that kind of problem in Vancouver, which is a terrifically expensive residential market, is more efficient multimodal transportation for service workers to come to the city from outlying areas. Seattle doesn't have that advantage, so it's important to invest in transit.

The panelists agreed that ST3 would be a good thing for the region as well as Downtown, which will get four new stations and a tunnel. The plan will offer Seattle an opportunity to develop around new transit nodes. Given the current prosperity of Seattle, now is the time to make improvements in mass transit. It's expensive, but it's a key component to Seattle's future, in Downtown and elsewhere in the region.