Today the official website for Nyaruko-san: Another Crawling Chaos, also known as Haiyore! Nyaruko-san was updated to reveal the first key visual for the second season of the series as well as what the second season will be called. The visual can be seen to the right (click the image for a larger version) and the second anime season will be called Haiyore! Nyaruko-san W.
As for what the W stands for, it is currently unknown though it is worth noting that the first season of Haiyore! Nyaruko-san contained many references to past anime series and this may be the case with the title as well. Anime studio Xebec will return to handle the second season and all of the main staff are returning to voice the characters. The Nyarko-san: Another Crawling Chaos anime is currently un-licensed in the West, although English subbed episodes are currently available on Crunchyroll.