During recent decades, rapid urbanization, an increase in population, and a change in lifestyle have generated a significant amount of waste electrical and electronic equipment (WEEE). To develop sustainable and efficient WEEE management policies, particularly in developing countries such as Vietnam, it is of paramount importance to forecast the amount of WEEE generation expected in the future. In the input-output approach as one of the WEEE estimation models, the determination of EEE lifespan is a major concern because it can be dynamic with time and vary with socioeconomic situations. Therefore, three scenarios were considered on the basis of the association of lifespan with gross domestic product per capita. By considering the lifespan transition, this study estimated the potential amount of WEEE, particularly large home appliances including refrigerators, washing machines, air conditioners, and televisions generated in Vietnam and the relative volume of obsolete metals contained in the WEEE during the period 2015–2050. For this, it employed a population balance model, logistic function, and Weibull distribution. It was found that the estimated weight of WEEE discarded in Vietnam during 2050 is mitigated 50% under the case where the lifespan transition is considered, compared to the case where the lifespan transition is not considered. By considering the relationship between lifespan and GDP per capita in estimating potential WEEE, this study to some extent covered the uncertainties related to the lifespan and can consequently contribute to the enhancement of e-waste estimation.