Here is the official statement: https://support.bittrex.com/hc/en-us/articles/115003571832-Statement-on-Ignis-IGNIS-airdrop-to-Nxt-NXT-holders
To sum it up they basically said that will support the airdrop, if you had NXT on the day and time of the Snapshot (2017-12-28, 00:00 UTC if I'm not mistaken) they will give you 0.5 Ignis for each NXT you had in your wallet at that time.
What they don't state is when will it happen, because they have to setup and test the wallet first. Based on what they did with Qtum, and GeoCoin tokens (links below) it will probably take about a month or less.
Last, the price listed on coinmarketcap and HitBTC was a futures price, pumped up by speculation, good thing is it set a resistance for a little over 20 USD i think so a month from now they will be probably worth around 3-5 USD
RE: Ignis on Bittrex