It has already started when we've seen the quick drop coming from the ATH. However, you can see the huge difference from this year to 2018.
This wasn't as bloody hell as 2018 and this year is like setting a high low if you get the idea of that. We may go through again two to three years of dealing with another bear market until the bull run comes again.
Like it was in the past, many folks have learned their way and lessons for this recent bull run and they'll apply it when it's come again.
It seems Bitcoin is giving less ROI in every cycle. It's natural because the market is becoming more mature over time and big names and companies who are already professional in the economy participate in crypto. They can not be easily manipulated or panicked. There will be a time when bitcoin prices will move sideways or be volatile like a stablecoin. The opposite can happen too if demands skyrocket.