If we analyze the Bitcoin chart from the beginning of the year, we see that it has been bearish until April, and it is only afterwards that it has begun its recovery.
Can we deduce a pattern to be repeated each year, and take advantage of it?
There are many variables and angles, it can be difficult to attribute price trends to a single cause or prime mover. If it is true buyers were waiting for post april tax season to buy, the trend may not constant for next year. The combination of massive short selling on CBOE futures, coupled with big bitcoin dumps we saw near the beginning of 2018 might never happen again. We might never see the same price increase post april if bitcoin isn't devalued again post 2018.
Price trends can also become weaker over time. The first bitcoin fork announcement had a significant effect on btc price. The 2nd announcement had less of an effect. 3rd announcement was weaker still. The tightening of tax restrictions we witnessed late 2017 and early 2018 may have caught by surprise. Next year they could have far less of an effect, or no effect at all. Its premature to say which cycles will be consistent and which will be one time things. Only time will tell.