Increasing materially in numbers stored? No. By selective car type? Perhaps?
Frac sands are not coming back, so those car types could increase in numbers stored.
Coal will continue to decline over the next five years or more.
Tank cars? If oil trade prices stabilize around $45 to $60 a barrel (USA pricing), I would expect to see less crude oil being speculatively held. But that does not mean more crude oil moved by rail.
Crude oil by rail might continue to selectively be moved by tank cars -- but that is a speculator's market play. Too hard to forecast.
Chemicals so far into July are still negative volume-wise by rail year over year. The international market for chemicals must improve for US chemical tank car trade to improve. Into the fourth quarter 2020, I see chemicals being either down a bit or at most up by about 2% volume-wise year over year, same 3rd and 4th quarter timeline. Industrial production must significantly improve for chemical to grow. Too much uncertainty as of mid-July 2020.
NEW Auto Sales across most of the USA look to be in slow recovery -- and well below annualized monthly sales so far into July. That will lengthen the finished vehicle trade recovery period for rail movements. Again, how much family disposable income is left every month under these COVID restrictions to go out and spend buying new cars? Not anywhere near as much as last year or in 2018. Is there?
FUNDAMENTALLY, I share the opinion of others like David Nahass that the fog of war type COVID-19 and slow industrial recovery translated into a perhaps almost two-year low orders cycle for all new railroad cars of any type. That includes lower orders for double-stack container cars.