I doubt the Chinese will accept mass exodus. They will probably shut the border again, if refugees start coming in huge numbers. But if they don't, this could potentially be the end for the regime.
I think this decision was driven by the internal power struggle within the Chinese Politburo and not out of any particular humanitarian concerns.
Nah, but we do know that living conditions are pretty horrible, which is always a powerfull motivator for human action. The regime is also not able to shut out all info to the degree they used to do.
This decision is very clearly another slap in the face committed by the Hu/Wu faction in the Politburo against Bo Xilai's people since he was fired. From now they'll probably tolerate North Koreans who quietly make their way to foreign embassies or find menial jobs. They definitely won't tolerate a high-profile rush across borders. Kim Jong Un needs face, after all.
Besides, in many dictatorships the central leadership retains considerable popularity and the local officials are blamed for any problems. East Germany was a rare exception thanks to the widespread availability of western media. In North Korea, radio sets are pre-tuned to government stations.
Don't forget the in-house speakers as well.
