supposedly, QE is driving an asset bubble---including in bitcoin. logically, tapering QE would therefore imply a potential popping of that bubble. the fed chair just mentioned the possibility of tapering in late 2021 or early 2022.
fun fact: the term originally emerged when ben bernanke suggested in may 2013 (several months before the october 2013 bubble) that the fed might soon taper QE. they actually did reduce and eventually end QE in 2014, during bitcoin's bear market. https://www.thebalance.com/fed-tapering-impact-on-markets-416859
coincidence or not? who knows.