The Diminishing Impact Of Miners
I believe the Bitcoin four-year market cycles driven by the mining reward halvings will be a thing of the past quite soon. I believe this will be the case because of the following reasons:
A) The amount by which the block reward is reduced in each halving is halved each time compared to the prior halving. As the number of bitcoins already in existence grows, the impact (relative to the existing supply) of the halving on the supply of Bitcoin is more than halved each time.
B) Miners are increasingly becoming public companies that are no longer forced to fund their operations by selling most of what they mine.
Diminishing Returns And Lengthening Cycles
Benjamin Cowen discusses evidence for lengthening cycles in Bitcoin:
It seems pretty obvious that if the cycles are lengthening, the roughly four-year waves will be broken at some point and be replaced by other types of waves.
Institutional Investor Driven Speculative Waves
The last "mid cycle" peak last spring was a rounding and not a blow-off top like all the previous ones. We're probably going to see more of something like that going forward.
I would not be inclined to believe in the four-year cycle as before or to expect a sharp blow off top reaching the hundreds of thousands of dollars in the coming weeks or around New Year.
Conclusion
I do believe in a logarithmic long-term appreciation curve as the one above remaining valid for the foreseeable future, however. But I don't believe in predictable and regular cycles any longer. I would say whale behavior indicated by transfers in and out of exchanges is the best predictor of what is going to happen in the near future. It may be that if one does not wish to speculate, it might be an ever better policy to just HODL and completely ignore market cycles from now on.