Clean-slate network architectures have been proposed in the recent years as an alternative to the current IP-based architecture. However, a complete replacement of the current Internet architecture is a difficult and lengthy process. A heterogeneous Future Internet where several network architectures coexist simultaneously can be expected. Nonetheless, differences between network architectures raise inadequacies in the efficient sharing of common resources among the different architectures, creating large problems to Future Internet development and testing. This work proposes a framework, named Future Internet Fusion (FIFu), that unifies existing and upcoming network architectures, promoting a transparent interoperation between different network architectures and, consequently, the rolling out of new network architectures in an incremental and disjoint way. A proof-of-concept prototype of the proposed framework was deployed targeting IP and selected Information Centric Networking (ICN) architectures and evaluated over three different scenarios, with results showcasing its feasibility and its impact on the overall performance of the network.