I think there is a significant amount of belief that there will be another massive bull run in December. So, until then, I don't believe that Bitcoin will fall significantly below $6000, nor stay under $6000 for any long period.

If there isn't a huge bull run in December, then I think that market sentiment will turn even further away from belief in Bitcoin and all bets will be off. However, I expect there to be some sort of bull run in December even if solely because people believe it will happen. However, if there is a bull run, then I expect a crash in January and into 2019.

I expect that any bull run in December won't go to $20,000, because people buying now will be aware of the boom-bust nature of the market, and some will wish to take profits. If it was me buying at $6000 then I'd be very happy to sell at $10,000 to take a sizeable profit. If too many people follow similar strategies, then this in itself could prevent the market matching the previous peak.

However, how do you spot a sustained bull run in real time. If you watch a bull run too long by the time you buy in it might be near the end, and therefore no less risky than buying at the start of a bull run.

Note that I make no claims of ability to accurately predict the future. I make predictions to see if my current beliefs about Bitcoin are correct or not. They haven't always been. E.g. I thought that Bitcoin would fall significantly below $5000, but it didn't.