I think I actually agree, and to be honest, I wouldn't mind it.
I think it helped going into this feeling like Akira wasn't going to be around for the long haul, like I love their relationship and it is sweet but I never let myself get attached to them as a couple because I always felt like the the narrative was going to go more towards the route of helping Akira finally rest in peace. I'm not looking forward to some big miracle that he comes back to life or some twist that he was never dead, as from a storytelling standpoint, those are pretty weak plot devices. But who knows. If he does end up with the neighbor, I hope the guy gets fleshed out some more (am I wrong in assuming he was the one who actually took Haruto to the hospital? so maybe we'll get more character development for him when Haruto finds out?) If he ends up with Akira, I hope it isn't too kitsch.
I think if the author decides to let Haruto and the neighbor end up together it'd be a very wrong move from her. After all, she can't just focus on Haruto and Akira's pure love in the first many chapters and expect readers to not root for them until the end or for them to accept the neighbor as Haruto's new lover easily (well unless done smoothly). I'm thinking that since the neighbor can see ghosts (right?? Am I remembering this correctly?), maybe he is included in the story to help the main couple, not there to be Haruto's new guy. (Oh man if that's true many readers would be upset)
He'll end up with the neighbour.