After some inquiry, the USFS Region 8 has confirmed that it extended its cave closure order until May 21, 2014.
Observant cavers had noted that the previous order had expired on May 21 of this year, and no subsequent order took its place. We checked their website, and can still not find either the expired order, or the new one.
Some of the US Forest Service units have their own closure orders (e.g. Mark Twain National Forest, whose order runs until 2016). The Daniel Boone National Forest has a link to the order extension, and you can read the order here:
http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_032408.pdf
Other Forest Service units, as well as the Region 8 site, have no mention of closure orders, so it's hard to understand how the public, much less the caving public, would know that such a restriction existed.
However, I was sent a copy of the order today, and we will be posting it on the NSS' WNS website shortly.