It's important to note that:
* There are no concrete plans for a sequel: While there's been some speculation and fan interest in a sequel, there has been no official confirmation from Netflix or the creators of the show about a "The Last Airbender 2."
* Casting is not usually done through open auditions: Typically, casting for major film projects involves talent agencies and extensive casting calls for specific roles, rather than open auditions for the general public.
While it's exciting to imagine a sequel and see Toph back on screen, it's best to avoid believing unofficial rumors and wait for official announcements from Netflix or the creators.