There are no important support levels in the 3500-5800 area, so the weakening of BTCUSD can continue up to the bottom of the range even without fight.
However, it is worth paying attention to how the market players behave near $3500. This is the area of reversal to growth in September 2017, so the forces to look closely at the dynamics near these levels.
If falling stops, it could sign for reversal. And cautions traders should wait for another confirmation sign for buying.
It is also important that mining in wide range of world regions is becoming unprofitable, and we saw 600K Bitcoin miners were shut down in last 2 weeks, F2Pool Founder estimates.
In the future, this will stabilize the supply, but short-term can also be a good signal for the market.
So long BTC/USD falls we should pay attention to the volumes as their decline will talk about the end of the downward impulse, as fewer players are connected to the sale.