As stated above - there would still likely need to be an option to open the door from those not using a phone or watch. So either an NFC keycard and/or keypad.
Also - investing in the technology is still an expensive proposition. One that isn't necc likely to see the ROI hotels want - even with the added value of being able to marketing to customer (customers they already know they have because they have their reservation and personal info already, etc). They can already push offers to their customers.
The travel industry (hotels and resorts) are making great strides in their marketing and desire for personalized experiences (and contextual marketing) however they are still very much in their infancy. NFC-based locks isn't going to be a driver to spend that kind of money - yet - for many. For those hotel chains that want to be cutting edge, they might for cool factor. But I don't see the technology hitting critical mass for quite awhile within the industry.
ETA: However it will be a nice convenience for those hotels that have facilities, etc that would also be used in conjunction with the access function. IE - Vegas hotels, resorts, etc - where you can use your watch to unlock your door - but also at the various on site restaurants, spas, tennis, bars, water sports, etc as a method of payment. But again - the adoption rate won't be instantaneous by any stretch...