I would say Miraxus because Lucy and Laxus are never meant to be. Lucy and Laxus dont even talk to each other so its pretty obvious that they are not gonna end up together. Miraxus is probably the best bet as Mira and Laxus are close in a way. Besides they are an adorable couple <3
Best guess would be Mirajane. There are barely any moments where Lucy and Laxus interact. And btw Lucy already has Natsu. But again if anda think about it I don't think there is gonna be any pairings at all. I mean the Anime hasn't focused on any pairings so far.....well except for Levi and Gajeel.