The activation height for NU7 has not yet been set.
NU7 is planned to be the ninth major network upgrade for Zcash. For an indication of what is likely to be included, see the NU7 Candidate ZIPs at zips.z.cash.
If NU7 includes major consensus changes as expected, then it will not be supported by zcashd. In order to prepare for this upgrade, you will need to upgrade to the Zebra consensus node developed by the Zcash Foundation.
Zebra is an independent Zcash node implementation written in the memory-safe Rust language. Since Zebra was implemented from scratch in an async, parallelized way, Zebra is currently faster than zcashd. It is consensus-compatible with zcashd, and Zebra and zcashd nodes will co-exist on the network in the run-up to NU7.
Zcashd is being deprecated and will be replaced by the Zebra full node. Migration is in progress — see the Zcash Z3 updates thread for current status.
If you are unsure about how to switch from zcashd to Zebra or how to upgrade your Zebra node, don’t worry! The Zebra Book should answer most upgrade-related questions.
ASIC miners do not verify consensus rules, and it is likely that NU7 will not alter the block header, so there’s no specific upgrade action needed on their part. They rely on the mining pool they’re connecting to, which is responsible for upgrading its nodes.