If they eventually come around to accepting you and start showing you respect and make the effort to bond with you…you’d only make matters worst by giving them the cold shoulder. In the process, you could hurt your marriage as well.
If the in-laws didn’t show up at your wedding…they were showing (through their absence) that they disapprove. BUT MORE THAN THAT…they ruined their own reputation before the many guests that attended the wedding. Many of the guests must be thinking “What kind of parents would be SOOO PETTY as to not even attend their own son’s wedding?” For such small pettiness…they made a fool of themselves. From their absence…they lost more than they gained.
Also, even if the in-laws didn’t show up…you had more than enough people (from among YOUR immediate family and relatives and friends) who love you, who wish you well, and wanted to share in your joy. They make up for your in-laws. Plus, maybe their absence was better in a way. Perhaps if they had been present…their angry looking face and cold actions would have embarrassed you and the guests.
If you look at the OVERALL situation…the in-laws embarrassed themselves, strained their relationship with their son, spent so much time being bitter. They lost so much…(so much more than you)…that it’s better to “bury the hatchet” if they eventually “come around”. I know it’s easier said than done, but try to be the bigger person.