Well given that a lot of things have already hinted towards it, than it is highly likely, but until its confirmed by the park themself than it is purely speculation. I take everything said about this ride with a pinch of salt as Towers have been known in the past to send enthusiasts down the wrong paths
Whilst I completely agree that it's still only speculation at this point, and not totally on board with a lot of the wicker stuff, didn't Merlin file a copyright registration for "The Wicker Man" during the demolition of The Flume? I doubt they'd go as far as to file an entire copyright for the name seeing as we haven't even heard from Towers themselves in this case. As well as that, it was tweeted by a construction firm working on SW8 that the ride was due to be a "Wickerman ride", so it seems unlikely that the copyright is for another Merlin park or attraction.
I'll also put my two cents in on the whole wicker theme seeing as it's come back up again. I strongly believe that if the ride does turn out to be a Wickerman ride, it will have no connection to the movies, but rather have its own back story relating to the Pagan ritual itself.
The copyright claim was filed by Lane IP, which represents Merlin on copyright grounds. They also worked with Merlin when copyrighting The Smiler and other recent attractions.