Will Issei eventually end up with Rias.
I heard the writer of the novels said he wants to have an harem ending, but after some more research, i saw that she became his fiancee and afterwards on the wiki i read that she doesn't mind him having a harem.
But what makes me unsure is ofcourse that anyone can change a wiki page,
I also noticed a person saying Rias would eventually become his wife. But im just really talking about issei having actual feelings for her outside of the harem thing ( which of course is still going to happen)
I really haven't found some concuslive proof on the subject though, the wiki here titled her as a fianciee and said that she accepts Issei's dream of having a harem.
After all, in that perverted head of his he showed some real affection for Rias throughout the series ( the whole season 1 thing wasn't just loyalty and family promise, that part was obvious)
Im ok with spoilers too on the novel side of things if it helps build up your argument.