I think this is a new article about Detroit-style pizza. Detroit-style pizza really seems to be growing in popularity.
There is no doubt that the Detroit style pizza is growing in popularity, but I wouldn't try to read too much into the article you cited. It is basically a PR release that was attibuted to PRweb.com, which is the vehicle that Shawn Ranzazzo has used to promote his company, the Detroit Style Pizza Co, and the Detroit style pizza that his company promotes, along with that style of pizza that Cloverleaf Pizza, which his mother bought from the previous owners, makes.
The Detroit style pizza market is not all that large. According to the Pizza Today 2011 Hot 100 Independents list at http://www.pizzatoday.com/magazine/2012-october-independents-list
, Buddy's annual sales are given as $20M. That is a number that I also found elsewhere from a research of corporate business data. Shield's annual sales are given as $6M. Elsewhere, I saw an annual sales figure for Loui's of about $1.1M. I was not able to find any data on annual sales for Cloverleaf or the Detroit Style Pizza Co. Neither is on the Pizza Today list although those companies may have chosen not to reply to the Pizza Today survey. Both Shield's and the Detroit Style Pizza Co have stated that they plan to expand their businesses, mostly through franchising. By contrast, Buddy's has grown its business organically. And it opens a new store only when business conditions and the economics justify it. With its national acclaim, they could easily have gone to a franchising model and done so successfully. Maybe that will happen some day but for now they seem to be content with things just as they are. Loui's is now run by Louis Tourtois' son (also named Louis), with no signs of expanding beyond their single store that was started by the elder Louis after he had spent 27 years with Buddy's and seven years at Shield's. He is now in his late 70s and putters around the store from time to time but it is his son who now actively runs the business.
By contrast, Jet's, which makes a square pizza with a lot of similarities to the Detroit style pizza but without calling it such, reported most recent annual sales of $231,462,400 (http://www.pizzatoday.com/magazine/2012-november-top-100-companies-list
When I was reseaching the Detroit style pizza in general, I found that there were pizza operators specializing in the Detroit style pizza in several states outside of Michigan. Going strictly on memory, they include North Carolina, Colorado, California, Florida (a few locations), Minnesota, Texas, and Nevada. But, for the most part, they are one or two store operations. You can see the names of those stores at http://en.wikipedia.org/wiki/Detroit-style_pizza
although that list should perhaps be updated to include Pizza Square in Tampa and Tony Gemignani's place in California.
So, yes, the Detroit style pizza is expanding its footprint but I would say that achieving parity with the New York style and/or the Chicago style pizza is a long way away, if ever. Creating demand for a product that most people don't even know they should have is a very difficult proposition that can consume a great deal of time, energy and money.