i can picture it that in the year 2020, some scientist expose weak algo in monero hash that enable any transaction prior to 2018 to be exposed,
I think this Dr. Scientist will rather focus on some other coins. Monero is simple build it is not build on Bitcoin and then added anonymity with mixers. With those coins there is way more things where can go wrong and that way way more chances for Dr. Scientist get his results.
Monero will be most private coin in 2020 as it is today and as it was 2015.