Among all the challenges which highlight the need of reconfigurability in manufacturing systems, taking into account the introduction of a new product has been rarely considered by the researchers. Indeed, taking into account the new product variants in the future production generation of the line at the initial design stage smooths the reconfiguration process of the line. This paper studies a mixed-model assembly line reconfiguration planning problem where the line consists of several resources (workers and robots). This study aims to design a line which produces a given product family with a set of product variants, and a new product variant will be added after a certain period of time, named production generation. At each generation, the production family can change with the addition/removal of a product variant. Therefore, the line needs to be reconfigured at each generation. We propose a new Mixed-Integer Linear Programming (MILP) which aims to minimize the total reconfiguration effort, the total cost of designing and reconfiguring the line taking into account the buying, selling, re-assigning the equipment and resources in the worst scenario of possible product families which are produced in several production generation. The MILP is validated through solving a simple example, and the results are given.