The information about upcoming games is still very scarce, considering how huge a thing Touhou is. Independent developers generally love spamming screenshots, trailer videos, social media stuff all over the place months before a release. It's what people think marketing is about, but would it really add any value to a franchise like Touhou, where the actual playable games speak for themselves?
I've always appreciated the mysterious aspect surrounding Touhou releases, like how ZUN went through the trouble of blocking the new boss characters from the latest teaser screenshots. It leaves just enough room for speculation, and comes off as more personal somehow. Even seeing the cover art feels like something festive.