It took a year and a half to convert New Texas Giant, which is the same timeline we are looking at with Mean Streak's conversion. So the timeline is perfectly plausible, based on the conversion of Mean Streak's smaller Dinn Corp. cousin.
Spacing out the opening until 2018 will allow Cedar Point to focus all media attention on the conversion/expansion of their waterpark to the new Cedar Point Shores, which in turn would allow Cedar Point plenty of hype-train time towards the end of the season for a most likely ride announcement in the fall.
This also allows Cedar Point some inadvertent hype throughout the course of 2017. Roll the clocks back to season opening 2006; Skyhawk was the new ride. White Water Landing however had been removed during the off-season, with mysterious footers placed in the pond adjacent to Wave Swinger. So while the media was excited for Cedar Point's latest swing attraction... cement footers for a prospective future attraction made equal headlines. Cedar Point began construction on what-would-be Maverick in July of that same season, posting teaser signs, etc. throughout Frontier Town. That way by ride announcement, half of the work was already done for generating excitement and buzz for the new attraction. Dialing the clocks back even further, Millennium Force and TTD both started construction early/mid the season prior to their opening, before announcement.
While enthusiasts already know what is being installed, the general public will not, and will certainly be very excited to see the new track going in, and follow progress/inevitable announcement with bated breath as well.
All of which is to say, this is opening in 2018, with plenty of media hype along the way.