VIM4 needs vendor u-boot 2019.10 and Linux 5.4 kernel sources, which similar to the vendor Linux 4.9 kernel used with VIM1/2/3 might require nip/tuck but should be usable with recent Ubuntu userspace versions. There is currently no upstream (mainline) kernel support for what Amlogic calls the T7 platform and while A311D2 has a similar name to the A311D used in VIM3 it’s really a new SoC generation and there are some major IP differences that will require all-new code. The 5.4 base moves the vendor kernel closer to a number of modern kernel frameworks, although it sadly remains too-old to sensibly support panfrost (which needs 5.10 or an improbable amount of DRM backporting) so Mali blobs are needed, and the media drivers have been reworked towards V4L2 (amcodec is dropped). Amlogic started to upstream core peripheral support for S4 (S805X2) which is more of an evolution to G12B/SM1 but should be a precursor to SC2 (S905X4) which is closer to T7 (A311D2). From my own conversations with some senior people I’d say that Amlogic is similarly not-quite-committed to upstream support for this generation of hardware as they have been for previous ones; so it will probably happen, but not quickly, and emotive terminology like ‘plans’ and ‘roadmap’ should be skipped to avoid setting expectations 
6 Likes