The D.C. Circuit similarly struck down the rule last month. An interesting aspect of the Fourth Circuit decision is that two of President Obama's own appointees were on the unanimous panel.
While there is a chance the Supreme Court will take the case and side with the NLRB, I wouldn't bet on it. The NLRB poster requirement looks like it's done for awhile.
Image: Fourth Circuit seal is public domain as work of federal government. Not official use.