Hello, I'm new in MoTK, sorry if my english is bad. I've found out a lot of coincidences between Touhou games, so I think we could speculate about Touhou 16.
First, Touhou 9 PoFV. 9 is 3*3, and Touhou 3 was PoDD, so we had another Phatasmagoria game. Touhou 4 LLS. 4 is 2*2, so we had another shoot 'em up. Remember tha the first 3 touhou games were all different, so we could have an Arkanoid instead of a shoot 'em up. So, I think Touhou 16 could have a gimmick like LLS, because 16 is 4*4.
The * indicates a multiplication, at least in my country, so it may confuse you.
14 is 7*2, so we had Sakuya in DDC, just like in Touhou 7 PCB. So, Touhou 16 could have playable characters like Touhou 8, teams of characters from the most recent fighting game, ULiL. Touhou 12, UFO, had a more proper relation with the PC-98 than EoSD, again, 12=6*2.
Anyway, it's also possible to have Reimu and Marisa as the Stage 4 bosses, like Touhou IN, and LLS.
So, I guess Touhou 16 would have a relation with the PC-98, have teams of playable characters from the most recent fighter, have Reimu and Marisa as the stage 4 bosses, may need to do a 1CC to see the good ending, may have relation with Mugenkan or the Lunar plot, may have Last Words, and may have a returning character, from PC-98 or Windows; if there is a plan rather than just coincidences.