This is probably going to be long-winded, but here goes:

Unfortunately, Tulsa just isn't big enough to be able to lure MLS in the same way Houston did. Before AEG/Phil Anschutz moved the San Jose Earthquakes from Skelly-esque Spartan Stadium to a zero-sum gain at UofH's Robertson, Houston actually had the highest TV ratings for MLS games of any non-MLS city. And Houston is a top 10 Nielsen market; Tulsa is #61.

If TU had gone with a grass field over artificial turf for Skelly Stadium in the mid 90s, Tulsa most likely would have been a charter member of MLS (we really were THAT close). And we could have kept the team a good 5-10 years before MLS would've started demanding local ownership and eventual construction of a 20,000 seat capacity soccer specific stadium. Or we could have been "contracted" from the league the same way Tampa and Miami were a few years ago.

I'm pretty sure Skelly Stadium was part of the Tulsa package presented at last year's MLS Cup in Frisco, TX. That proposal would have included the plans for a soccer stadium for downtown's East Village/East End. If the Kansas City Wizards team had moved to Tulsa last spring, you woulda seen the same stadium wrangling going on in T-town that we saw this summer in KC and Salt Lake City... threats to move those teams to Philly... or St Louis... or to the new soccer specific stadium in Rochester, NY... oh, and there's going to be a very important vote in Overland Park, KS on funding a youth soccer complex/stadium for the KC Wizards in the next couple of months...

The "Houston model" includes plans to eventually build a soccer stadium in conjunction with Houston ISD at Delmar Stadium. FC Dallas currently shares Pizza Hut Park with Frisco ISD. A Tulsa team could possibly share a 20k-capacity soccer stadium with Union, or Jenks, or BA, or Owasso... seems it's only a matter of time before one or more of those school districts builds a stadium like that anyway... this year's "Backyard Brawl" woulda fit nicely in a 20k seat stadium complete with luxury boxes built to MLS specs...

Look no further than down the turnpike in Edmond/UCO for an example of what MLS wants:
http://www.nmnathletics.com/PhotoAlbum.dbml?&PALBID=2951&DB_OEM_ID=7300

But since Express Sports balked at adding another 10,000 in seating capacity to the visitor's sidelines/endzone and ended up buying the Redhawks anyway, OKC/Edmond didn't get a team.

I recently watched "Once in a Lifetime; the story of the New York Cosmos" on ESPN2 last week. There was a part of the documentary that argued the old North American Soccer League the Tulsa Roughnecks belonged to died mostly because it had overexpanded. There was a snippet of highlights that included a few scenes from Skelly Stadium, accompanied by this: "We (the NASL) had no business being in San Antonio, TX; Jacksonville, FL; Memphis, TN; Las Vegas, Hawaii, Calgary, Edmonton... all became stops on the Cosmos' traveling circus..."

Conspicuously missing on that list was Tulsa. Nobody who knows the NASL regrets having a team in Tulsa. Which is why Tulsa seems to be mentioned often in MLS discussions while none of those other cities get the time of day...