The USPTO records are searchable for any trademark application, whether it was accepted or not, and whether it's live or dead (as of today). Searching for "amusement" and either "Cedar Fair", "Cedar Point", or "Kings Island", I cannot find a trademark application for DB, NOR can I find any suitable application for DB that was made around the 2008/2009 timeframe. This was surprising to me--if anyone can find a trademark for Diamondback, please show me.
As for MT or Banshee, both of those DO have trademarks, but neither had any other suitable trademarks filed around their respective times. For what it's worth, MT's trademark application was filed 1 day after it was announced, but Banshee's application was filed about 3.5 months before its announcement.
I'd welcome @silver2005 to show us what other trademarked names were filed for these 3 coasters. Perhaps my search isn't as extensive as it can be. I'm always looking to improve! BUT, for what it's worth, I'd guess that multiple trademarks were not made for these roller coasters prior to opening as I believe my research on USPTO's site is extensive enough to uncover these. @ldhudsonjr, I wouldn't give up on hope though. As seen with MT, GateKeeper, and likely some others, the trademark wasn't filed until the day before/of/after the coaster was announced. There's certainly some precedent there that the same could happen with this coaster. IMO though, either 'Polaris' or 'Orion' will be related to this project.
Below is an example of one of the searches. Results are listed in order from recent to older.
It's worth mentioning that the '325' in Fury's name was applied for after 'Fury' was ('Fury' was applied for on 1/23/14, while 'Fury 325' was applied for on 6/9/14).
Originally, the 'Fury' trademark was filed in January 2014. At the end of April 2014, the USPTO sent a letter to CF for an initial refusal of the trademark application, citing "likelihood of confusion" with Sperian's line of eyewear (seemingly, they had glasses that also shared the 'Fury' name). Behind the scenes, CF and Sperian reached an agreement that neither of their similarly-named trademarks would be confused with each other. CF readily signed this agreement on 5/23/16, but Sperian did not sign until 6/16/16 (shown below). I'm speculating that CF was beginning to get anxious waiting on Sperian to sign the agreement as they went ahead and filed a new application for 'Fury 325' on 6/9/14, about 1 week prior to Sperian's signature on their agreement.
What I'm getting at is I don't think '325' was initially intended to be part of the coaster's name. An issue came up with the trademark application of 'Fury', and while at the end of the day the 'Fury' trademark was awarded to CF, CF didn't want to wait around for a possible second refusal, so they went ahead and filed for 'Fury 325' separately, which sounds better anyways IMO. As for I305, I'm guessing CF just didn't want to pull a Six Flags and have two different coasters under the same name.
EDIT: (so I'm not double-posting)... @ldhudsonjr & @collin.klopfstein, the 'crest' you all were referring to is just a metal louver in the station building. These are used for ventilation. That's not to say there won't be a crest added, but what's shown in the blueprints is simply a vent for the hot air rising to the station's ceiling. On one page of the blueprint, it even says 'louver' in the notes off to the side. Below is an example of one I found on a house, a bit more decorative than the one shown in the blueprints, but still serving the same purpose.