Difficulty is based on how meany nodes are on the network, correct? Growth will slow when miners realize it is unprofitable to mine, at the same time the value of the Bitcoin will go up thanks to increased scarcity.
It seems to me that the Bitcoin was not designed for stability. Oh well, just means you can make a ton of money real fast... but also lose it.
"Never assume malice when it can be explained by incompetence" Heinlein
I doubt if it was "designed" to do any such thing - such are the hazards of exploring unknown territory!
HUGE profits and HUGE losses!