When we rejoin the Hawkins crew in the fourth season, we find out pretty quickly that Lucas and Max have broken up (several times, in fact). They've both got their own issues that have contributed to their growing apart: his attempts at trying new things and new social groups in high school, her family trauma and lingering guilt over Billy's death.
However, it's clear there are still feelings between them, especially in the aftermath of Max's near-deadly encounter with Vecna, during which several memories of Lucas help her escape Vecna's clutches. If any of the "Party" members are likely to reconcile, we'd say it's probably these two.