I reckon the CBeebies Land Hotel will be very popular. Merlin have essentially plugged the final gap in their hotel lineup: Alton Towers Hotel for adults/older families, Splash for families with children about 6-12 (or people benefitting off the cheaper prices), EV for families looking for something unique and now CBeebies for their youngest visitors. I would expect to see CBeebies rooms leave the other hotels, possibly an SW8 room will go in of them for 2018?
However, I've got concerns. Not so much about the Hotel, but this focus on CBeebies Land instead of everywhere else on Resort! There are some areas which need TLC and new attractions, especially Mutiny Bay and Dark Forest. X-Sector I've heard is meant to get some work done on it this closed season so that isn't as much of a worry to me.
Also, I'm quite conscious that Merlin also haven't opened a fully new thrill installation since 2013 (Galactica was just an upgrade). Alton Towers has relied on Passholders a lot more since the 2015 incident and I think not adding something new on the thrill front risks alienating them. Let's hope 2018 is a good year and possibly more than just one thrilling attraction is added!
EDIT: Something else just occurred to me. Towers seem to be putting all their eggs in one CBeebies themed basket. Especially with the funding cuts the BBC has received/will receive, doesn't that put Towers in a risky position? After all, CBeebies Land attracts people who like the IPs, if the IPs disappear then Towers don't get as many customers.