I think it's been taken as a slight against Portland that I didn't include them in the poll, though I also didn't include San Diego, the proposed second New York team, or other possibilities. Some of the teams I included (please don't blame Luis, I put this latest poll together) I'll admit I did so more as a curiosity than as a practical possibility. I love the idea of a Las Vegas team - how bizarre is that?
Anyway, part of the reason I didn't include Portland is because it's a city that seems to like its USL team, the Portland Timbers. That loyalty may actually work against an MLS option.
No USL team has ever moved up to join MLS. Realistically speaking, why would a successful USL owner want to pony up millions of dollars to join MLS? It's a league that loses money, and he (or she) would have to take on part of the league's debt and in return, get less individual control over how to run their own franchise. If an owner is doing well in USL, the temptation to stay there may be too strong.
To be a part of MLS requires very deep pockets, because even as many teams are becoming profitable, and the potential for more revenue builds, costs are also climbing.
Having a successful USL squad in town may also push away new incoming investors. What usually happens to USL teams when an MLS organization moves in is that the USL squad falls on the proverbial sword, sacrificing itself rather than trying to compete with its upper-level cousin. Upon the announcement of Toronto's MLS team arriving in 2007, the USL team, the Lynx, dropped two levels down to essentially become a quasi-amateur squad - a PDL team.
The Utah Blitzz won the USL second division title in 2004, but disappeared completely once Real Salt Lake came on the scene.
It's likely that part of the reason those USL teams decided to throw in the towel versus MLS was because they believed it wouldn't be much of a contest, competing against the glamour of the top level of soccer in the US and Canada. Thing is, Timbers fans are among the most loyal in USL. I'm not sure many would agree to giving up their beloved squad for some generic Portland S.C., just to join MLS.
Beyond the impression that Seattle would far more readily sacrifice the Sounders for an MLS upgrade (this is what I was told, so please don't think I've formed this opinion of Seattle fans myself), the buzz I caught at the All-Star game was that Qwest Field makes Seattle more of a practical option in the short term. Not sure exactly why PGE isn't considered as viable a location. Maybe it's the whole sharing with baseball, artificial surface thing.
Also, I was specifically told that there are more investors interested in Seattle as an MLS city, so simple deduction raises the odds of a bid being successful.
In the end, though, it's all about the deep pockets. Whoever steps up with the credibility of big-time funding will get the team. In other words, if billionaire Paul Allen decides he wants to join the soccer movement, and he wants the new team in Seattle or in Portland, that's likely where MLS will go.