FlyerTalk Evangelist
Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: BA Silver, TK E+, AA PP, Hyatt Globalist, Marriott LT Plat, Hilton Diamond
Posts: 13,033
Expect to lose 20k if you do anything in 2020 that requires cancellation or ticket re-issuance.
I expect that a pure date change (exact same route, carrier, etc.) would still be fine, but there are no guarantees with TK.