I'm on a search committee for an assistant professor of product design position at a major research university right now, and I see a lot of bad information here.
Most art schools do have tenure tracks, as do universities and community colleges actually.
But what I want to address specifically is that you need a terminal degree in the field. There are 2 options for design, you can do a PhD or an MFA. To be clear, the MFA is unique to the US and is a 60 credit studio program, from the investigation I've done, it's actually very similar to the newer European practice based PhD's that take 3-4 years to complete.
The MA or MS is not a terminal degree, and will not qualify you for tenure, or anything more than adjunct teaching in many situations provided you have a good deal of professional experience. A lot of people like adjunct teaching though.
The school I am at, and at which we are searching, is a D1 research institution, meaning that we want someone to be able to teach, which oddly every designer thinks they can do with little or no effort (sort of like architects and photography). In addition the person needs to be able to create and drive an agenda of scholarly research and creative production with client work alone not being adequate.
Good luck in your search, I'm finishing the MFA in the spring, and am already interviewing for Assistant Professorships. I think like anything else, the degree is what you put into it. I disagree with a lot of people here, the MFA is worth it, if you are prepared to be serious and open minded about it. It's not a repeat or substitute for a bachelors in design, I've seen some people come through here thinking they are just going to have 3 more senior years of studio, being left along to just perfect their commercial level work, that isn't really the case though.
One more thing that might be a bit disappointing though. Most PhD and MFA programs have already concluded their application processes for next fall, they tend to be due in Mid December and Mid January. Start studying for the GRE depending on where you want to go, and think about what your goals are for grad school.
Just some guy, trying to figure it out too.