What is the future of international migration flows? The growing availability of bilateral international migration data has resulted in an improved understanding of the determinants of migration flows through the estimation of theory-based gravity models. However, the use of these models as a prediction tool has remained a mostly unexplored research area. This paper estimates simple gravity models of bilateral migration flows for the whole world and projects these models into the future. We focus on a particularly hard-to-predict country, Spain, which evolved from an emigrant-sending to an immigrant-receiving country, and compare the estimates from internationally available data to those coming from local sources. Our results show that the projections of migration flows depend more heavily on the span of the baseline dataset used to estimate the model than on the particular functional form and variables chosen for the prediction although we confirm the relevance of origin-country demographic factors.