segregated witness adoption What happens if segregated witness never reaches the 95% adoption threshold from miners? Will it still take effect for those transactions where the miners have adopted it?
By current agreement Segregated Witness will only activate after it reaches 95% of the miners signaling readiness. 

Sending Segregated Witness transactions before that would be foolish, as if they were to be included in a block, anyone would be able to spend the outputs before Segregated Witness is enforced. They are however, non-standard to current versions of Bitcoin Core.

If the 95% threshold is not achieved for an extended period of time, there might be a proposal to lower the threshold.