At some point we'll have a 20%-40% retrace in my opinion, the difficulty is timing when.
Everybody is waiting for this retrace and shorting while the price rises.
When they are forced to close, the price goes up further, it's a vicious cycle.
Add to this the Tether FUD on Bitfinex with people buying up BTC with their Tether to withdraw it from Bitfinex and I think it explains the intense buying pressure we are seeing right now.
Timing the top will be difficult, as we just casually walked through the biggest resistance on the way to 20K in my opinion, which was the 6K to 6,8K range.