No one can answer that question at the moment. In my opinion, Natsu isn't ready for a relationship yet, and sees both Lucy and Lissana as friends.
However, I believe that it would most likely be Lucy, mostly because Mr Hiro has been giving hints here and there in the manga. Plus, Lissana seems like she has given up on Natsu, and even approves of his and Lucy's relationship.
Besides, I think it's very obvious where the Fairy Tail shippings are going. I think even the anime agrees.
Speaking as someone who hates Nalu and is opposed to the Lisanna hate within the fandom, I don't think Natsu is ending up with Lisanna. It's kind of ironic that they seemed to have more chances when she was thought to be dead, but when she was actually brought back, the Nali ship just grew more and more irrelevant each day, it can't even compete with Nalu anymore.
Although Natsu had "history" with Lisana and sorta liked her when they were young, I do not think he sees her anymore than a friend now because of the two years that she had "died". Besides, I think he had grown feelings towards Lucy and vice versa for many reasons and Hiro had given many hints in the anime and manga about NALU. Also, I don't think Natsu wants to be in a relationship right now, but if he does, Lucy has a better chance than Lisana.
