The device is quite promising but the 4K + is still our flagship device, so it’s where support and development primarily go.
The new Pi looks great, price considered. Unfortunately it’s a bit of a chicken and egg problem, so there won’t be hardware video acceleration, HDR, HD audio until Kodi v19 is released which will be at the end of 2020 or in 2021. We need a V4L2 pathway for that to happen. There’s progress in Linux 5.2, but that hasn’t been released yet. The Pi 4 will stay on 4.19 for a while for the sake of stability.
Some codecs need to fall back to software decoding / are not supported in hardware (VP9 (YouTube 4K), VC-1, MPEG2). This means they are effectively limited to 1080p. The focus on 4K for HEVC makes sense however.
By 2021, I suspect things will have moved along quite a lot for both devices.
It’s a nice upgrade over the 3B +. As the device is a significant revamp, you can expect some bugs for a while.