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.
Why not? People expecting a bull run have bought in already, meaning that they won't be adding much or any buy support to the market at all. If you also take into consideration that most of the people expecting a bull run this year are noobs, there isn't much to rely on here. People need to forget about bull runs and move on. If people can't deal with this market they are free to sell and leave.
Even if people are invested, they often can still buy more. The price is $6320 as I write. If it goes down to $5700, then I expect some of the people currently not buying to fill their boots even more. Also, not everyone may have bought coins yet. E.g. It's also quite possible that there are people who missed the previous low waiting for it to go lower, but will snap up at $5700 (as an example price) if it happens again. There are people who believe in both a December bull run but also that Bitcoin will fall much lower than $5000. Those people may not yet be invested, but still may do so at a higher level as December draws closer.
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 don't think you know how bull runs work. They don't happen because people believe it will happen, because that means they have bought in already as stated before. Bull runs happen when no one expects them to happen and people fomo in hard. You know what happens if there is an attempt to initiate a bull run right now? People will dump their bags and quickly undo whatever had to become a bull run.
Sentiment is everything in a market such as Bitcoin. For there to be a sustained bull run, then prices need to start going up, but those who bought in at lower levels (including those holding now) to hold during the bull run to prevent the supply/demand ratio getting too high. Otherwise people will just dump as you say, as has happened in the recent blip we've had, and several similar blips during the year. So, belief in a extended bull run in December, which is certainly frequently expressed, can certainly influence whether any bull run at that time becomes a sustained bull run.
In your discussion, you seem to be assuming that there is only one type of investor - e.g. that everyone who believes in a December bull run will already be fully invested in Bitcoin. This is an over-simplification of the situation.