Apple soft releasing updated versions of current firmware is nothing new. They did this with the 4S iOS 5.0.1 (9A405) where they released 5.0.1r1 (9A406) directly after due to certain models having "No service" or "No SIM" issues. These updates were sent to the affected phones OTA (if possible) and updated automatically.
Most likely they are fixing something related with their data network otherwise they would just release an update for all devices to patch the jailbreak exploits. However, because the jailbreak requires physical access to the device (unlike the jailbreakme.com exploit) it's unlikely Apple will patch these exploits any time soon. Apple knows about the exploits and how to easily patch them, that's a fact, but for whatever reason they've chosen not to patch them.
*EDIT*
Rumor circulating around is that the update has to do with AT&T's data network. Not much is actually known yet.