As for criminal contempt, can you imagine the U.S. Attorney for Washington, D.C., Holder being his or her boss proceeding to arrest the AG, I cannot, but perhaps my imagination is overly limited. As to congress taking the AG to court, via the filing of a civil action against him, that too might be something of a hoot, though stranger things have happened, or could happen.
We're in uncharted waters here. The US Attorney has the power to prosecute Holder, but he also has discretion on the matter. I really doubt he's going to pursue it.
As far as the civil side of things, it could take years.
In neither case does Congress really have a way to compel him to produce the documents in a reasonable amount of time. Given the invocation of Executive Privilege, it doesn't look like there's any pressure from the top.
So, basically, we just got treated to a day of political theater and little more.