I've heard this before.
There's another conspiracy that America is in on this. That apparently the overthrow of the Chubby One is imminent, and his replacement by a close relative will lead the road to reunification. This deal was apparently chalked between all the big powers.
Yet another conspiracy, held mostly by the Chinese citizens, is that the US wants NK to keep their Nukes because it gives them an excuse to keep a heavy military presence in SK and Japan.