BIP 141 doesn't require 100% of blocks to signal for it for it to activate.  Its threshold is only 95%.

If 1916 blocks signal SegWit, it's definitely going to lock in regardless of what happens with the later blocks.

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At this point though, it would require pretty much every single miner in existence to coordinate not to signal SegWit, which is almost completely impossible.  There are only 4 blocks to go.