Rentier state dynamics have enabled PGCC governments to elevate citizens’ welfare through sustained reliance on oil revenues, reflected in SPI levels that consistently exceed the global average. Yet existing scholarship remains predominantly backward-looking, overlooking the structural vulnerabilities embedded in rent-dependent economies that may threaten the long-term stability of welfare gains. This study addresses this gap by adopting a forward-looking lens, forecasting the five-year trajectory of SPI to evaluate the future resilience and sustainability of the PGCC’s rentier welfare model. The aim of this study is to examine and forecast the Social Progress Index as a representative of citizens’ welfare for the years 2023–2027 in the member countries of the Persian Gulf Cooperation Council. The independent and predictive indicators of the study were selected separately for each country from among the World Bank development indicators using the EDR feature-selection method. The SPI index was forecast for the years 2023 to 2027 using the XGBoost machine-learning method. The forecasting model of the present study, with a MAPE of less than 2 percent for the test data, indicates high accuracy in predicting future values. Examining the predicted SPI trends in the six countries shows that the United Arab Emirates, Bahrain, Kuwait, and Saudi Arabia will experience an almost stable trend over the next five years. It is predicted that Oman and Qatar will observe a fluctuating SPI trend. These results suggest that welfare indicators in PGCC countries have reached a stable level and will not experience further growth over the next five years.