Our current guesses are:
Wind: In a couple of days
Water: 22nd of April
Light: Mid-July
Dark: Mid-September
The encyclopedia in Sanahtlig's toolbox gives you a quick peek on all the upcoming SSRs.There is a persistent rumor about that, but I've never seen it happen. Or heard it happen to anyone. So I don't think you can.
You have several days before the next event - just farm Nike's Rampage and buy Vine from the store. The breakpoint for Vine being better than Medusa is pretty damn low, you should be hitting it if you've invested into your Dark grid at all.