A priest friend of mine and I were discussing this recently and I agree with his opinion: the litany should be said (or at least the prayer of the litany), but there should be no dismissal. There's no point, since we don't expect them to actually leave. So why say it?
It's an anachronism. If we suffer persecution and it needs to be revived, then we can revive it, but there's no real point in doing it now. All it does is confuse people.
But in some parishes, we do
expect them to actually leave. My fellow catechumen and I were told to leave at this point, and we returned during the Litany of Thanksgiving. We would stand or sit outside, discussing our explorations, reading, prayer lives, and so forth, as we grew into Orthodoxy. If some, or even most parishes choose not to do this, then that is their choice, but it seems to me that if a priest does away with a long-standing custom of the Church, then realises that this leaves an inconsistency between the words said and the actions done, then it is somewhat perverse to remedy this by omitting the words instead of restoring the custom. That's how traditions get eroded.
Your priest friend reminds me of a priest I encountered on a forum similar to this one, who was theorising about reforms to the Divine Liturgy, and listed a number of points, giving his reasoning and some academic background behind each point. At his parish, he always omits the troparia on the Beatitudes (which I know happens in a number of parishes), and his proposal in this theoretical list of revisions was that the Beatitudes ought to be removed from the Liturgy altogether because they are a vestige of a procession that no longer takes place, and that while they could remain if they actually reflected the feast or saint being celebrated, they do not, so they should go. The fact is that they do
express the feast or saint if done properly. He was abbreviating the Liturgy by leaving out the troparia, and then using the effects of this abbreviation as a justification for omission.
Both examples reflect a sort of thought process that I don't really understand.