This isn't very surprising. The dozens of times in which Hiro has Natsu's face shoved into Lucy's boobs should tip anyone off that Hiro obviously wants to draw some NaLu. When they were working on the movie project, Mashima's first response was to draw the NaLu hug. They came up with the plot working backwards from that picture. Mashimap prioritized drawing a NaLu hug over the actual plot of the movie.
In a recent interview(video in spoiler), Mashima said he was going to work more romance into the series and I wouldn't be surprised if
all the major pairings start receiving massive fanservice. Like Gajeel and Levy are confirmed to have children. Gray is probably going to confess to Juvia after this arc. We already know Jellal and Erza loved each other for like 300 chapters. Natsu and Lucy is pretty much the last on this list, and I think most of us can guess that Lucy probably likes Natsu. I would be surprised if Fairy Tail ended with a major wedding between one of the couples, with some of the other couples already having children.