On Sun, Sep 27, 2015 at 7:50 PM, Peter Todd via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

10) Waiting for nVersion bits and CHECKSEQUENCEVERIFY will significantly
delay deployment of CLTV

It's been proposed multiple times that we wait until we can do a single
soft-fork with CSV using the nVersion bits mechanism.

nVersion bits doesn't even have an implementation yet, nor has solid
consensus been reached on the exact semantics of how nVersion bits
should work.

Small correction, the suggestion is to aim to roll out CLTV+CSV together by 0.12 release, using IsSuperMajority() (or versionbits if it is ready by then). If CSV is not ready by then, we'd just roll out CLTV.

However, the CSV related pull requests are ready for final review and if that can happen soon I don't see why we wouldn't roll CLTV+CSV out together before 0.12. A considerable amount of time, discussion and iterations have occurred for the related PRs and I believe they are at the point of consensus modulo final review before merging.

References:

Mempool-only sequence number constraint verification

https://github.com/bitcoin/bitcoin/pull/6312

Mempool-only CHECKSEQUENCEVERIFY

https://github.com/bitcoin/bitcoin/pull/6564

Mempool-only Median time-past as endpoint for lock-time calculations

https://github.com/bitcoin/bitcoin/pull/6566