The church is constituted as a new people who have been gathered from the nations to remind the world that we are in fact one people. Gathering, therefore, is an eschatological act as it is the foretaste of the unity of the communion of the saints.
Since both the departed saints and we ourselves are in Christ, we share with them in the 'communion of saints.' They are still our brothers and sisters in Christ. When we celebrate the Eucharist they are there with us, along with the angels and archangels. Why then should we not pray for and with them? The reason the Reformers and their successors did their best to outlaw praying for the dead was because that had been so bound up with the notion of purgatory and the need to get people out of it as soon as possible. Once we rule out purgatory, I see no reason why we should not pray for and with the dead and every reason why we should - not that they will get out of purgatory but that they will be refreshed and filled with God's joy and peace. Love passes into prayer; we still love them; why not hold them, in that love, before God?