I think bitcoin will go into a bull run when halving comes because as far as I know the last time bitcoin experience halving, its price increase rapidly and that's why people are now focusing on their hodl because they know that there's a bull run that going to happen in 2020. But of course no one knows what will going to happen because like I've said before, bitcoin and other cryptocurrencies are so volatile and decentralized that you just need to take a risk in order for you to have a good money in the future.
Usually people are bullish in anticipation of this event and then sell after it happens or just before.
In the long run halving is great and will increase the value of bitcoin but for this process to kick in some time has to pass. New mining equipment will have more power and be more expensive to run making fresh bitcoins much more valuable but the whole economy won't double in value just like that because rewards got halved.