Is BIP 146, which defines using the low S value, still on the docket to be signalled and implemented given that SegWit fixed the
txid malleability issue by moving the witness outside the transaction? I'm asking because it can fix the
wtxid malleability which now requires re-syncing of transaction data when it is changed from what it was originally relayed.
Also, will the implementation be a soft-fork which would treat this transactions as non-standard but miners can still include them in the block, or will it treat the transactions with high S value as invalid?
Bitcoin-core already enforces low S-values as a standardness rule for transaction relay, but making a transaction non-standard does cause a softfork.
BIP-146 does call for a softfork by making high S-values in tx signatures invalid, not just nonstandard.
The BIP also states that the majority of txs on the network already adhere to the low S rule, as of Aug 2016. To quote from it:
The reference client has produced LOW_S compatible signatures since v0.9.0, and the LOW_S rule has been enforced as relay policy by the reference client since v0.11.1. As of August 2016, very few transactions violating the requirement are being added to the chain. For all scriptPubKey types in actual use, non-compliant signatures can trivially be converted into compliant ones, so there is no loss of functionality by these requirements.