If you want to really know why people say 3k BTC it's because of this.

The 200 weekly EMA is at about $2500 right now. Pulling back to that should be considered perfectly normal. since the 200 EMA is still in an uptrend, a slow decent down to it might suggest we bounce off of it around 3k. It's perfectly feasible to believe that 3k BTC will come to pass. Does that mean OMG it is dead? No, quite the opposite, 3k BTC would mean it could resume quite the uptrend again.