I think if BTC goes near to $20k a massive sell will occur, which will drop the price below $15k. Maybe on 31 december the high will be around $19k, with a low of ~$17.5k, but even if it stays around those ranges for a couple of days I think it is possible to drop to ~ $15k since people who bought now will take profits, which will crash the market ~ 20%. Only time will tell :/