There are two points to be made:
1) The concept of schar veoineash in the coming world by definition cannot be the ultimate motivator. It is basic human psychology that a long term pleasure (or the opposite) cannot truly overcome immediate gratification. Of course it can be a motivator, but not an ultimate one.
2) the real motivator has to be one that gives immediate gratification, and that is the connection that one has now and every second with HKBH, and the more one cultivates it, the more pleasure one experiences through doing the mitzvohs etc.
It wold be of great use for the chinuch system to teach the Chovos Hatilmudim, and Hachsheres Ha’vreichim, which clearly exlplains the ins and out of this concept.