What good did Moshe promise Yisro now that he did not promise him in Pasuk 29?
Rashi: Although the Torah does not explain what the good was, they later gave Doshnah (the fertile land) of Yericho
See Ba'al ha'Turim.
Rashi: As the Pasuk states in Shoftim, 1:16). This land was given to Yisro's descendents until the Beis-Hamikdash was built, at which point it was given to the owner whose land was appropriated to build the Beis-Hamikdash on it.
Even though he is not mentioned there, but in other places in Tanach
Who had the last word? Did Yisro remain with Yisrael or not?
Ramban: Moshe had the last word
Ramban: As stated in the Yerushalmi Bikurim 1:4 (Refer to 10:32:1:1**).
Seforno: As the Pasuk testifies in Shoftim, 1:16.