It was supposed to be a part of one, until the studio went into bankruptcy and ended up being partially owned by New Jersey.
The story behind KoA is absolutely nuts. They wanted to make an MMO sequel, with R.A Salvatore still on the writing, but due to bloat and mismanagement, ended up massively in debt and plans for a sequel got scrapped.
Has Phoenix Wright been a documentary about the Japanese legal system this entire time, and we just wrote it off?