We seek to solidify a permanent role for FPGA in future datacenter servers. While we envision a new breed of FPGA devices architected to this role, it will nevertheless retain the complete essence of being an FPGA—spatial, highly concurrent, finely controllable, and reprogrammable—to maintain its differentiating and complementing strengths over current server hardware and software. As such, we embrace the current Stratix 10 sectorized tile-based fabric as the basis of the proposed Crossroads 3D-FPGA. Our research looks for innovative extensions to this baseline with both programmable and hardened features in support of the Crossroads 3D-FPGA objectives. Architectural innovations will pursue three major thrusts: (1) incorporating an NoC in support of both long-haul intra-FPGA interactions and server dataplane switching (with inline processing); (2) leveraging 3D integration for new capabilities to enhance the flexibility and power; (3) supporting a virtualized application execution environment for temporal and spatial multi-tenancy.