Do you think there will be some love stories in the future in SNK or nothing of that kind will ever happen ?
No. Isayama made a deliberate decision early on that the manga would be better without romance. In a Dec 2013 interview, anime director Araki said of Isayama, “I’ve never heard anyone else so openly declare ‘It’s better without those elements.’” (source: @fuku-shuu)
Unless something has radically changed, a few canon crushes and hints at romantic feelings are all well get. My hope is that if any relationship become canon, maybe the epilogue will let us know.