Hmmm, hard to choose between IRIS and Lillie, i remember that the others had some hints to have potential love for some other people (like rivals , drew ? Of the competitions where pokemon do dance stuff, i forgot the names)
Edit:
Examples: Brock with Misty? (I know that Misty liked ash many times but in many anime they put something similiar and in the end the unexpected couple appear)
Dawn x Zoe ?
May x Drew