Responses
+ there's love brewing by Luca & Princess Charlotte, so either way he'll still get the title.
He doesn't need to be heir of anything, just live happily this time
beta
I didn't read the novel, but isn't the most probable scenario is the child of Judith and Ruedger will the next heir of Winterward.
And considering Luca will retain Maibaum from mother side, he can instead inherit all the titles/lands left by Margarett, the former king's sister, as he said he'll transfer those to Judith, but Judith will marry to Winterward family.