Hi hi!
As with any champion, unless we've officially announced/teased a skin, it isn't something we openly discuss as devs. The State of Skins Dev Diaries are your best bet for spoilers for what's coming up further down the road, as opposed to what most of our social channels tease for the next patch.
The main reason is, a lot of things change in development - a concept may be heavily changed, ice boxed, or scrapped entirely. We may want, I don't know, Candy King Shen (no idea why, but for the sake of example), and that doesn't work (surprise), so we want like, Star Guardian Shen.
If I said we were making Candy King and you were super hyped, you'd be pretty upset that we pivoted so heavily on thematic. It'd also suck for me to say, 'hell yeah, new Shen skin coming this spring!' and have one of the other aforementioned things happen and then you don't see anything on PBE.