I think it’s almost a cast iron certainty Cedar Point will be opening a coaster for the anniversary. They are having a quiet investment year next season so they will most likely go big for the anniversary. So I would personally recommend waiting for the anniversary year (plus I myself will be going back then too!)
In terms of “when to visit weather wise”, any time in August would be ideal really given the long opening hours (this chances on the last week of August as it is considered “off peak” so the park closes earlier at 8pm) the lines ofcourse will be long but if you are investing in fast lane plus anyway, this won’t be an issue. Be aware though they do seem to do a Merlin with fast lane and oversell it (Steel Vengeances fastlane can still easily clock in at over an hour)
For flights, I flew to Iceland first before getting a connecting flight to Cleveland Hopkins. Both flights together are around 8 hours worth of flying time. From there it’s a one hour drive from Cleveland to Sandusky.
Hope this was some sort of help!! Cedar Point is the best park out there so it is definitely worth going.... don’t even think....just go!!