Usually weekends, the market is slow, volume is low so I don't think there will be movement that we might see the price going down again. We are hovering on the $20k level, and as high as $21,700 yesterday so we might have seen the lowest low at $17k'ish but we shall see. Still good time to buy and no need to wait to like $15k. A good advise is to do DCA'ing.
The lowest support point is still at $17,700 and this is a strong support point, if it breaks it will touch the $15k area as you mean. The market is still playing in the $20k-21k price area, hoping this will be the start of the bitcoin market getting better. Doing stargei DCA is indeed recommended, but also adjust it with the money reserves you have. Waiting at some of the lowest support to buy bitcoin is certainly an option, don't panic too much to buy, make sure everything is in accordance with the strategy that has been made.