I have a feeling that whatever ride they're building to replace Volcano is a "go fast" program. Remember, Volcano's removal was unexpected and it certainly feels like the park wasn't really ready to take the ride out of service. I bet someone was making phone calls nonstop to a bunch of manufacturers immediately after the park made their decision to axe Volcano and saying "what can you design for me asap?" The quickest way to do that is to see if a stock, or close to stock model fits in your plot of land. If it does end up being a close to stock model, so be it - I'm certainly not going to complain about a new B&M no matter the size. They could easily pull a Six Flags and build a semi-permanent spinning mouse instead.
Also keep in mind that Cedar Fair has been alluding that their CapEx spending will be limited in the near future since they've taken on quite a bit of extra debt with Schlitterbahn and that resort in Sandusky. I wouldn't be surprised to see CF pull a Six Flags and start installing more medium sized coasters instead of these enormous monstrosities like Orion. The CapEx faucet won't shut off - the chain does need, to a certain extent, to replace the rides it removes...but if the chain is savvy, they could get two or three medium sized coasters for the cost of one Orion. Doing so would satisfy lowered CapEx strategies and replacing old, high cost rides with low ridership.
The only people that'd be unhappy would be the enthusiasts because every park won't be building another Fury every year...oh wait...
The point is that it doesn't matter if your biggest competition is right next door - if the other park has something that you don't, they have an advantage. It's not a situation like Cedar Point and Kings Island where they're part of the same chain and it's in their best interest to offer complimentary ride lineups.but that's what six flags does.