This is a difficult question to answer as there is no easy way to purchase Reef cryptocurrency. The best way to buy Reef would be to find a reputable exchange that offers it. However, at this time, there does not seem to be any exchanges that offer Reef.
Additionally, there is no way to directly buy Reef with fiat currency. The only way to acquire Reef would be through mining or by purchasing it from another user.
Since there is no easy way to buy Reef, it is unlikely that it will be added to Coinbase in the near future. Coinbase typically only lists cryptocurrencies that can be easily purchased and sold on their platform.
Therefore, unless Reef becomes more easily accessible, it is unlikely that Coinbase will add it to their exchange.