2001 Acura MDX VTM-4 failure

I asked the dealership to diagnose a intermittent clunking / rumbling sound that seemed to be coming from the engine compartment. They changed the rear differential fluid but that did not resolve the problem - based on my research this response is pretty typical. The mechanic then informed me that it would cost over $2000 to replace the rear differential and he did not recommend it. His recommendation was based on the fact that continuing to drive the car would not cause more damage / increase the ultimate cost of repair. He also said that the failure mode would not be catastrophic (a breakdown) and that, in fact, I would simply lose the traction control feature. The car would then function as though I had a standard differential. Do you agree with his analysis, forecast, and recommendation? Is the noise likely to worsen or ultimately disappear when the there is a complete failure? There are no other indications of a problem beyond the intermittent noise - the car drives fine and there are no alarms.