HitBTC will support nxt airdrop and will issue ignis token to nxt holders:
https://forum.hitbtc.com/discussion/2477/will-hitbtc-support-the-ignis-airdrop-for-all-nxt-holders
https://blog.hitbtc.com/statement-on-the-upcoming-btc-hard-forks-and-ignis-airdrop/?utm_source=media&utm_medium=twitter&utm_campaign=btc_and_ignis

I expect next will be bittrex and poloniex