I'll be jumping up and down too; it's boys' provision that is the bigger problem and, having a DS and living close to the Wildernesse site, I'd be livid if KCC failed to deliver for local boys.
For Trinity to start building, a site leasehold agreement would need to be finalised first; and given the intention that Trinity and the grammar share areas of the site and some facilities, the contract must surely particularise aspects of shared arrangements including each party's undertakings and obligations. That will bring the reality of a grammar annexe much closer.
Perhaps one of the reasons for the perplexing delay to Trinity's building programme is lack of agreement on the contract?
I think KCC will want WoK in the annexe regardless of whether a boys' sponsor school is secured and will seek to introduce boys later - either after liberalisation of statutory provision for grammars, so that the WoK annexe is converted to a standalone co-ed grammar or, as I've suggested in a different thread, by WoK consulting all parents again on the co-ed issue in a year or two, when the girls' annexe is established and more Sevenoaks parents are part of the parent body of the school.
Of course, WoK have already changed their admission criteria so that, for 2015-16 entry, Sevenoaks children are given equal category A location priority (or whatever they call it). Sevenoaks parents will therefore be a bigger group next year anyway, and I am sure some will represent the needs of Sevenoaks boys in future consultations if nothing at all happens as a result of the current consultation.
I just wish that WoK governors would present you and other current parents, JJ123, with a clear outline of the pros and cons from their perspective. Perhaps you or parent rep's could request that? The governors and school management team must have been through a considered evaluation process at the time of the first consultation; so providing you with a written outline of their considerations should not take too long.