Or HaChaim on Genesis 49:8/אור החיים על בראשית מ״ט:ח׳

1 יהודה אתה יודוך אחיך, "Yehudah- as to you, your brothers will praise you, etc." Why did Jacob have to add the word אתה when he addressed Yehudah? Apparently the word was meant to exclude someone else. Besides, why did Jacob not say: וידך, "and your hand, etc," instead of simply: ידך, "your hand?" The same applies to the missing conjunctive letter ו in front of ישתחוו לך.

2It appears that Jacob's intention was to assure Yehudah that contrary to the blessings for the other brothers which were predictions for the distant future after Israel would take possession of the land of Canaan, Yehudah himself would already experience the esteem of his brothers. We have confirmation of this in Chronicles I 5,2 where we read: "for Yehudah became more powerful than his brothers and a leader came from him." At the appropriate time, Yehudah's hand would be at the neck of his enemies. At that time his brothers would prostrate themselves before him and he would become their king. This prophecy was fulfilled during the reign of Saul when David won great victories and the Jewish people crowned him king.