Website says if you buy the tickets at the hotel then still guaranteed admission, but they are not doing Happy 15 entry.
4.Admission tickets Admission to Tokyo
Disneyland® or Tokyo DisneySea® requires fixed-date park tickets. Hotel guests are able to purchase, at the hotel where they are staying, a single 1-Day Passport (ticket valid for entry from 8 AM) per person, per night, that can be used at either park during their stay, excluding the day of check-in. *To purchase park tickets, we ask that personal identification documents (driver license, health insurance card, etc.) be presented for every adult. *Please note that Open Tickets, Annual Passports, Revisit Passports, etc. will not be admitted. *Tickets can also be purchased at the Disney Hotel Service Counter on the 2nd floor of the Tokyo Disney Resort Welcome Center. *If park tickets are resold for a profit, this will be considered a violation of the terms of use, and these tickets as well as all tickets purchased by the person who engaged in such reselling activity (regardless of whether they were resold or not) will be invalidated and entry into Tokyo Disneyland / Tokyo DisneySea with those tickets will be denied.
5.Hotel guest benefits The following hotel guest benefits will not be available until further notice. ・ Happy 15 Entry privilege ・ Guaranteed park admission (unless tickets are purchased as described above)