Purpose: This study aims to explore how high-density urban development interacts with the evolution of green infrastructure networks and to examine how different future policy pathways may reshape ecological connectivity in Seoul. Method: This study uses land-use/land-cover data for 2000, 2010, and 2020 in Seoul and integrates the PLUS model, Morphological Spatial Pattern Analysis (MSPA), and circuit theory to analyze the spatiotemporal evolution of the green infrastructure (GI) network and to simulate its differential responses under four 2040 scenarios: NDS, UDS, EPS, and BDC. Ecological sources, corridors, pinch points, and barrier points were identified, while network performance was assessed using static centrality indicators and dynamic resilience tests under random and intentional disturbances. Result: The results show that from 2000 to 2020, built-up land in Seoul increased from 57% to 60%, while ecological land continuously contracted. The GI network exhibited a high-cost maintenance pattern of connectivity, with increasing source fragmentation, rising resistance surfaces, and concentrated connectivity risks. Under the 2040 scenarios, NDS, UDS, and BDC continued compensatory connectivity, whereas EPS improved structural optimization through source integration and resistance restoration, but showed stronger core-node dependence and lower robustness under intentional attacks.