According to The Business Journal 22 different cities in the US and Canada have the accumulated wealth to support an NBA franchise:

On Numbers focused on 57 metropolitan areas that do not have NBA franchises, analyzing their total personal income (TPI), the amount of money earned by all residents in 2010. Click here for the complete methodology.

An NBA team, according to the study, requires an income base of $34.2 billion for adequate support. Twenty-two open markets are above that threshold, earning perfect scores on a 100-point rating scale.

Seattle, for example, has TPI of $176.1 billion. Its baseball, football and soccer teams need a combined base of $137.5 billion, leaving $38.6 billion in available personal income, more than enough for the NBA. 

From the methodology article:

Structure: Our system is based on total personal income (TPI), the sum of all money earned by all residents of an area in a given year. We used official TPI data from 2010, the latest year for which statistics are available from the U.S. Bureau of Economic Analysis.

We used team revenue data and average ticket prices to calculate the amount of TPI needed to adequately support a team in each league. Minimum income bases were estimated to be $85.4 billion for MLB, $37.6 billion for the NHL, $36.7 billion for the NFL, $34.2 billion for the NBA, and $15.4 billion for MLS.

We then calculated each area’s available personal income (API) by subtracting the TPI needed to support the market’s existing teams. Philadelphia, for example, has TPI of $281.5 billion. But its five existing franchises (one in each sport), need a base of $209.3 billion, resulting in API of $72.2 billion.

Capacity scores: Our final step was to determine market capacity ratings for every area, using a 100-point scale. Ratings are based on a market’s percentage of the necessary API for a given sport.

A score of 100 indicates that a market’s income base is sufficient to support a team in a specific league. A score between 70 and 99 is a sign of a borderline income base, meaning that a market may or may not be able to support a franchise, depending on the team’s ability to reach fans beyond the metro area’s boundaries. A score below 70 indicates that an income base in insufficient for a given sport.

The top five cities ready for an NBA franchise are:

1)  Riverside-San Bernardino, Ca

2)  Montreal, Canada

3)  Bridgeport-Stamford, Connecticut

4)  Las Vegas

5)  Virginia Beach-Norfolk, Virginia

Some personal thoughts:

1)  The article doesn't effectively identify pre-existing markets.  Several of the cities listed are already included within the media market of another NBA city, for example Riverside-San Bernardino is actually apart of the LA market.  Therefore, an additional team dilutes the NBA following rather than providing an additional media market, something I'd imagine the NBA owners are staunchly against.  After reviewing the list, 10 of the 22 teams 'ripe' for NBA expansion are already included within different NBA markets.

2)  The article does not gauge local interest in the sport, therefore should be viewed with a speculative eye.  Using college sports as an example, each region and conference has varying degrees of local interest.  The ACC and Big East have strong basketball followings with weak football, the SEC and Big-XII have strong baseball traditions, while the Big-10 has stronger hockey affiliations.  Lacrosse is widespread amongst the East coast teams, with limited influence out west.  This illustrates that different sports have different levels of success within the same market based on local interest.  Specifically, I question the local interest for Pro Hoops in Montreal.

3)  The article does not address NBA quality facilities.  The NBA left Seattle and may leave Sacramento not because they lack wealth or fan support, rather they lack quality NBA facilities.  Any potential NBA city would need to address the facilities question, and I'd speculate most on this list lack an NBA arena.

Although, the article claims 22 cities are ready for an NBA franchise, in reviewing their method and results, I thoroughly question the merits of the study.  Accumulated wealth is definitely a factor in determining where an NBA franchise should be placed, but as a sole indicator it lacks credibility.  Plus, weren't we supposed to have an NBA Europe by now?