MediaTek has just announced the MediaTek Dimensity 1300 that may be featured in the OnePlus Nord 2T/3.
This SoC is built on TSMC’s 6nm process featuring 8 cores which include 4x Cortex-A78 cores (1x Ultra running up to 3GHz and 3x Super running up to 2.6GHz), and 4x Cortex-A55 efficiency cores that can scale up to 2GHz.
Moreover, the GPU is a 9-core ARM Mali-G77 MC9. It can also support up to 168Hz refresh rate displays up to FHD+ resolution. The chipset can be paired with up to 16GB 4266Mhz RAM and a UFS 3.1 storage.

The ISP has support for up to 200MP cameras that can capture multi-person portrait mode video and 4K HDR video alongside hardware-accelerated AV1 decoding for faster 4K streaming.
No official statement has been released by MediaTek regarding which devices will feature the Dimensity 1300 chipset as of now.