For the short term, the Big 12 has stated that it is content with ten schools, and invited West Virginia on the premise that the Missouri Tigers were leaving for the SEC. Though Mizzou hasn't officially left the conference, the SEC mistakenly posted an official announcement (pdf, h/t Rock M Nation) of Mizzou's acceptance on its website Thursday night, before pulling the announcement down 30 minutes later and issuing an apology.
West Virginia's entry and the conference's claim that they were staying with ten schools means that other reported schools interested in joining the Big 12 - namely Louisville and BYU -- will have to wait for their invitation... but as we know with the ever changing landscape of college athletics, that could change at any moment.
ESPN's report says that West Virginia will have to wait 27 months before leaving the Big East - the same stipulations put on Pitt and Syracuse's move to the ACC -- meaning the Big 12 could have nine schools next season, if Mizzou joins the SEC alongside Texas A&M this summer. [Ed note: the Big 12 official announcement says WVU is joining the conference next year]
Either way, let's welcome West Virginia into the conference and say hello to West Virginia's SB Nation blog, The Smoking Musket.