Several towns within Route 128 have "gentrified": the housing stock got more expensive and/or upgraded and the people living in those houses shifted in terms of the kinds of jobs they had and how much they are paid.
The author asks, who is next? and proposes a series of characteristics to look for:
Good enough schools, commuter rail, a range of housing stock (starters and high end) and "personality": "Things like festivals, farmers markets, and a decent downtown are all part of this."
The comments thread is a little weird. Someone brings up white flight (which did happen in Boston, but has been operating in reverse for quite a while now). People talk about the credit bubble (which was obviously real, but there are areas within 128 that were impacted very, very minimally by the collapse, which suggests it wasn't that much of a bubble there. Of course, there were areas within 128 that took a big hit, too.).
The biggest confusion in the comments is the difference between "will it gentrify within the next 10 years) and "has it already gentrified". Arguments of the form, but it's had these characteristics for a while and hasn't gentrified yet are missing the point. Boston-Cambridge-Somerville gentrified before, say, Arlington, because distance is an overriding factor (walkable is best). If towns closer than Arlington are gentrifying later than Arlington, it's worth trying to understand _why_; several of the towns being pointed at (Revere, Lynn) are really obviously in the process of gentrifying, but have (and may still) suffer(ed) from airport proximity issues.
In general, towns and neighborhoods near Boston which have not "benefited" from the return to the city of People of Means with Children have not "benefited" because of issues like this.
There is debate in the comments about the actual impact of an MBTA station. The idea seems to be if the station has been there all along, why would it suddenly matter now? Which sort of makes me want to go, wtf? Been to a gas station lately? When people were buying a decade ago, gas prices weren't anywhere on their list of concerns and commute distance only mattered in terms of time. Not the Same World Now.
There's a lot of ambiguity in the term "suburb" as used in the comments especially. People are using it to mean places that I would call "city neighborhoods" (the East Boston remarks, for example), as well as separate towns.