Any privacy coin with a solid development team will be a good bet for 2018. But I think Sumokoin is also moving quick and paving the way in the privacy coin space. For example, they were the first to implement botnet resistance https://github.com/sumoprojects/sumokoin/pull/10.

We are petitioning Zaif exchange to add Sumokoin. Reddit thread is here if you would like to help:

https://www.reddit.com/r/sumokoin/comments/7l656h/lets_get_sumokoin_added_to_zaif_exchange/