I don’t think there will be titles in the cards for them. I mean, whatever for? Charles has set the monarchy on a course with less working royals - even though by accident. H&M stepping away, PA being an idiot his parents dying…. If they really wanted to up the members of titled associates they would probably have a look at his cousins Zara (personal or via Mike), Peter (via his father), or the Wessex. I also don’t see the Middletons taking on any royal jobs apart from accompanying the children when they perform a royal duty. We won’t see Carol handing out Wimbledon trophies anytime soon.
A title would be a big honour and certainly helpful but I think Wiliam would always choose the crown rather than the in laws. Now that a smaller RF gets finally established it wouldn’t look good if he suddenly hands out titles for their support. Maybe a spot in one of the orders.