I don't know if that was ever oficially said or not, but "phasing out" would be the logical assumption.
During Team Summit time frame, Scott posted something about the new Plus dishes (500+/1000+) and a statement about retailers managing their stock of SuperDishes. Also their is suppose to be a "Repoint Kit" coming out that will convert the SuperDish 121 to a Dish 500+ or Dish 1000+.
So it appears that users of Sat 121 will have to eventually pick up Sat 118.7; unless Dish plans to continue 121 and 118.7 to feed the SD-121 and the Plus dishes with the same programming.
EDIT:
Back to the original post....
The SuperDish 121, is larger than the Dish 500+/1000+, and may provide a better signal if he was to upgrade to HD (Sat 12) in the future. But the drawbacks are, he would need an "Unavailable Repoint Kit" to upgrade the SuperDish to receive 129 and need another service call (or several).
I agree with others to go with the Dish 500+. Then to upgrade, you would just add the bracket and DP Dual LNBF (and maybe re-peak) to receive 129. Hopefully, when they install the Dish 500+, they will leave the side bracket.