Luke and Reid had the perfect love. Unfortunately,the way the writers put it, Reid died just as Luke and Reid declared their love for one another. Thus their love was at its pennicle and most high. For this reason Reid will always be the "true" love of Luke's life. Even if by some morbid thought Luke and Noah got back together, Noah would always be second best. As Luke himself said, Luke and Noah were not right for each other; Luke and Reid were right together. Noah will always know that he could not compete with Reid and only got Luke by default. Furthermore, because the relationship ended at it's pennicle, it will always be perfect. There were no bitter fights, abuse, or heartache caused by the other person (except for Reid's death of course). And of course since Luke and Reid never actually made love but were extremely hot and steamy when just making out, you can only imagine what Luke's fantasies are in relation to that issue. No mere mortal could match that!!! It is close to impossible for a living person to compete with an idealized memory of an angel. So even if Luke were to love again, it would never come close to or replace his everlasting love for Reid. Thus as the writers put it, there are no winners in this triangle. Reid is dead, Noah at best can only be second best, and Luke will be kept warm by his memories and fantasies of the perfect love. How utterly depressing!
So if Nuke fans take some solace in the hope that Luke and Noah got together in the future, it is a hollow victory and somewhat sad fate for both Luke and Noah ;(