I think this could be grounds to be a little more optimistic than that! Vintage cars rides tend to take up quite a bit of room, and many companies have removed them to build roller coasters before; I believe Kings Island removed their original one to build what is now Backlot Stunt Coaster, and didn't Busch Gardens Williamsburg remove one to build Griffon?
Cedar Fair also recently said that they are spending $140million on CAPEX in 2020; there was a thread created on the forum! The only major investments I can think of within the group for 2020 that we know about are the Kings Island giga and the hotel for Carowinds (I think?); a giga and a hotel combined would probably only come to about $50million at most. Using that number as an approximate benchmark, that leaves about $90million that's being spent elsewhere; with that amount of money, any park is a prime candidate for a major investment, and that includes Michigan's Adventure!
I'm thinking along similar lines to @Coaster Chall YouTube
here; I'm not necessarily saying we should expect the next SteVe, but I could definitely see a lower-budget thrill coaster; maybe an RMC Raptor, or a Gerstlauer Infinity Coaster/Euro-Fighter?