One of the objectives of the IEEE Future Networks Initiative (FNI) Testbed working group is to collaborate with the vendor and research communities and thus expand upon the existing testbeds towards federated development of testbeds for next/future generation networks. This presentation will highlight identified challenges towards the evolutions of testbeds for future networks over 3-, 5- and 10-year horizons. The Testbed working group is also curating a directory of available 5G and beyond networking testbeds for use by both academic and industry research groups. The currently collected data suggests that there is a need to develop testbed federations and respective APIs. This presentation will show the aspect of identified diversity requirements and the challenges towards the development of scalable testbed facilities for future networks.