Since 1995 (the release of Toy Story), Debian has been using 15 names.
The first Toy Story had about 18 named characters (people and toys, both of which have been used for Debian releases), Toy Story 2 added another 8 names, and Toy Story 3 another 17 (I might have missed, double counted one or two). Toy Story 4 is in the making.
The stories have been adding Debian names at a rate of 2.04 per year and Debian has been using them at a rate of 0.71 per year.
Clearly that means that Debian will never run out of names to use, assuming that Debian will persist to exist and that Toy Story sequels will be made ad infinitum. Even if Toy Story 4 were the last and would not have any additional names we have enough names another 40 or so years of release of Debian.