Late new prediction!
In PMiSS, there was a section where various species and concepts were detailed that hadn't yet appeared in the series. As time has gone on, most new games since have revealed a new entry from this list:
Kappa
8 Million Gods
Celestial
Hermit
Divine Spirit
After Ten Desires revealed the divine spirits, the only entry left that has yet to have a part in a Touhou game is...Dragon God.
*SCARE CHORD*