'Au fur et à mesure' can be translated in various ways in English. It all depends on the context.
I would phrase your sentence as follows:
- little by little
- as you go along
- as and when
The old products will be gradually phased out as customers (start to) buy the new products.
I hope this helps.
"Old products will be phased out as clients buy new products." Or "old products will be phased out to the extent clients buy new products." The second version emphasizes more the idea of progression and can leave open the possibility that clients won't buy the new ones.The old products will be phased out "au fur et à mesure que" the clients will buy new products