What if dialogue leads to dropping the filoque? And where does the dialogue go after that?
Well, that would be a step beyond where St. Tikhon and Bishop Grafton of Fond du Lac got in the early 20th century.
From the Orthodox point of view, 'ecumenical dialogs' are an expression of 'love for heretics' (as I think Fr. Alexander Schmemann put it). Either we are just nice to each other and share views (which is from our POV a very quite form of preaching the Truth of Orthodoxy), or we're trying to determine whether or not their is unity of faith between the Orthodox and the other confession, in which case, union, or at least mutual recognition of orders and sacraments becomes possible. (Intercommunion for us is a natural consequence and sign of complete unity of faith.)
Until the Old Catholics followed the liberal Anglican approach to Holy Orders, there were serious Orthodox-Old Catholic discussions, which looked like they were heading toward union, then fell apart.
In the hypothetical circumstance where the Orthodox became convinced that a particular continuing Anglican group indeed confessed the Orthodox Faith, there might still be disciplinary and liturgical impediments to union: married bishops and the lack of an eclepsis in the BCP's Eucharistic rite come most readily to mind. (The Latin-style objections about 'validity of orders' probably wouldn't come up: whole dioceses of the (Nestorian) Church of the East were received into the Orthodox Church in the 19th century by confession of faith by their bishops.)
The filoque was unilaterally dropped by the ELCA with the publication of the new "Evangelical Lutheran Worship" hymnal. There was never an explicit theological or ecumenical review, just the up/down vote on the hymnal project trusting the Presiding Bishop to do the right thing on all matters theological and liturgical. Talk about a blank check! The ELCA should never have dropped the filogue liturgically without consultation with Rome.