Not sure if it could be an indication, but Ting is first substitute at Finlandia Trophy, Sonja nr. 2 and Ava nr 3. It would make much sense, because Ting hasn´t had an International yet, so I think it´s likely she would get one in Austria, she is also first subsitute for Budapest Trophy. Sonja is also substitute for Budapest Trophy, but lower on the list. It doesn´t have to mean anything, because Gracie wasn´t substitute before Nebelhorn, but we also know that she was busy the other weekends. Based on her recent performance, maybe Sonja will get a second Challenger.
But after Austria, there is also Warsaw Cup and Golden Spin, shouldn´t those count? Also there is Denis Ten Memorial in Kaz, that´s also before Austria. So basically I think there is still 4 Challengers left where US could send skaters and possible 6 spots up to grabs.