I would suggest speaking to a travel agent. Currently there's a lot to unpack in this....January is a lifetime away in travel right now.
Depending where you are sailing from quarantine may not be an issue. For example, right now if you were to travel to the UK, you need no test to enter the country, they have essentially declared the pandemic over. Should you test positive, and are denied boarding you can change your ticket and fly home, Canadians do not require a negative test to come home. Now if you were a US citizen, you need to have some sort of trip interruption insurance. Because you would need to cover extra hotel time etc until you either test negative or can get a fit to fly (notice of recovery letter) to come home.
If NCL denies you boarding, it may fall under a cancel for any reason policy, or trip interruption. BEST speak to a pro, and not risk your travel investment. Whether you prefer to go to something like CAA for just the insurance, or a TA is up to you, but things are changing fast still, better safe than sorry.