I don't think anyone will die, the 'last summer we spent together' doesn't mean that someone dies, maybe one of them just goes overseas (cliché), or they don't contact each other anymore, or whatever reason there is. I haven't read anything that could give me the impression of death being an option, maybe just sadness but suicidal thoughts haven't appeared once so far, don't go to the complete extreme guys
"The Summer You were There"
From the title we know, if the next summer could potentially lead to a bittersweet or nostalgic storyline. While it doesn't explicitly indicate that the story will be sad, it does set a tone that might evoke emotions related to memories and changes over time.
If, if the author really not gonna make it sad ending i think it'll not really fit, i mean after this much pain and end with happy ending? , nahh man it's just impossible.