Good question. For me, it will never stop because if it will stop no more people or miner will process our transaction, there are many transactions ever second. Blockhain is evolving everyday, you cannot stop mining because if it will happen, no more transaction will be processed.
Here I will agree with you. If the mining is stopped it means that the cryptocurrency will be stopped as well. Yes, Ripple will survive, centralized currency. I think mining will last for a LONG time.