It does not state how many residents have "traded their 4 bedroom family home" so they are not "isolated in their (4-bedroom) own homes":

Developers build projects for twilight years – Focus on amenities, walkable locations for over-60 set San Francisco Business Times – by Sarah Duxbury (see full article for non-Burlingame information))
The Peninsula's not getting any younger.
So it's a good thing there's big money going into senior housing developments in the area.
… Sunrise Senior Living has started construction on its 79-unit assisted living community on Trousdale Avenue in Burlingame. Sunrise already has four other Peninsula facilities open.
… While this seems like a lot of housing for seniors, the Peninsula's population over 60 is growing fast. According to state information compiled by the office of San Mateo County Supervisor Adrienne Tissier, 29 percent of Peninsula residents will be 60 or older by 2030, up from a projected 19 percent of the population in 2010. That's a 63 percent jump in 20 years, and a higher percentage of people over 60 than the forecast average for nine other Bay Area counties.
The market size alone is enough to make senior housing attractive to developers. That such developments seem marginally easier to get approved just sweetens the deal for those who have dipped a toe in senior waters.
From the experiences we've had in both Palo Alto and Foster City, there are lots of attributes to this kind of project that do make it easier … perhaps, to secure entitlements,? said Jeff Birdwell, president of the commercial division for Sares Regis Group. There's less (community) push-back for senior housing. It's much more like mom and apple pie. … There's a feeling you're doing the right thing and it makes sense.?
Politicians increasingly realize that senior housing is a niche and need that must be met. Supervior Tissier hosted a summit in May called Livable Communities for Successful Aging. Her hope is to come up with a series of senior-inclusive guidelines and best practices that cities in San Mateo County will consider for any future developments. If we continue to look at developing high density and transportation corridors, we need to think about seniors,? Tissier said. They're not necessarily a priority, but I don't want them to get lost in the mix.?
Senior housing is softer on a city's resources in some ways since it has no impact on schools, and traffic is minimal and usually off-peak. New housing for seniors could also help cities to reset their tax bases if long-term homeowners sell their properties to move into some sort of senior facility.
There's also the real need, one that will grow as baby boomers age.
While Mirabella and the Moldaw residences are in new mixed-use communities, most of the other coming senior housing will be along the Peninsula's established thoroughfares like El Camino Real and California Drive.
We're very excited about that market; it's a great location,? said Frank Rockwood, senior development officer with Sunrise, whose fifth Peninsula development is under construction in Burlingame. We would like to have twice as many communities on the Peninsula as we do now, and the reason we don't isn't because we don't think there's enough demand or timing. We are very demanding about getting the right location. … To get anything approved when we find that location literally takes years. These projects go way back.?
Sunrise is actively seeking additional Peninsula and Bay Area sites to develop.
Communities tend to embrace their elders, and many of us are growing older and recognize that need to provide a healthy environment for people to age and not just be isolated in their own homes,? Birdwell said. I think that's an easy concept for people to get their arms around and feel good about.?

– Written by Fiona