Prosecutors have appealed the judge's earlier ruling on perjury. Basically, it looks to me like the Feds don't have a case without this evidence. Anderson isn't going to testify, and if they can't introduce this evidence of Bonds' steroid use, prosecutors won't have anything to go on.
Legal Note: Normally you have to wait for a trial to be over to appeal. The idea is that if you appeal every ruling, you'd never finish the trial. Sometimes, though, you can file an interlocutory appeal, which is what this is. It's essentially a timeout in the trial.
However, this will irritate the judge, as noted in the Chronicle article. Trial was to start this week and the judge probably wants to (finally!) get rid of this case.
I predict that if the Ninth Circuit (the court that hears appeals from courts in California and other western states) doesn't allow this evidence, prosecutors will drop the case and Bonds will walk.