Board Thread:Manga/@comment-27096343-20151021150023/@comment-5774380-20151021163731

The text you are citing is from an interview a year ago: https://www.animenewsnetwork.com/news/2014-09-22/attack-on-titan-creator-isayama-manga-to-end-in-about-3-years/.79025

However, this year Isayama commented that the story is approximately "60% finished", and the last month his editor confirmed that it will last about 3 more years: http://www.crunchyroll.com/anime-news/2015/09/05/editor-discusses-beginning-and-end-of-attack-on-titan

That means around 30 volumes, not 20; so Isayama has plenty of time to address each storyline properly. Don't worry, we have Attack on Titan for a while, and each and every one of those questions will be answered in time. :)