After the first halving, the price shrank to 10% of the high, or 90%. Subsequent halving's had the price shrink to 20% then 15%, then 20% from that cycle's highs. 

My most conservative estimate is 15% down from this cycle high of 150k, at 22,500$. Others have suggested 40K or 50K bottom in the next bear cycle. 

I'll probably be wrong. With the ETFs and the halving pumping the price to ridiculous levels, really a historic event for boitcoin. Either way it will be interesting.