Why do you think they're putting skins on this patch that are set to release on 8.3?
Swain is the most highly anticipated VGU we have had yet. You can be damn well sure that Riot is going to capitalize on that anticipation as much as possible. And so, when he does, you can bet that there will be PLENTY of things to go with him.
They can only pack so much into one patch. So, 5 skins plus a MASSIVE VGU is probably a bit too much for them to handle. However, since Lunar Revel and Heartseeker skins are for specific, timed events, they need to get the skins ready sooner rather than later.
See where I am going with this?
EDIT: I will admit, it is speculation, but it looks very likely to me.