Until Cablevision relents or is forced by some new law, I don't see VOOM channels or any other Rainbow Media channels coming to FIOS. Just my opinion though and I have heard nothing new myself.
A tech I spoke with on a service call to my place said the Hicksville office/garage has the Voom channels and another CV employee said the channels appeared on the guide but only for a CV account. Maybe CV is going to finally give the channels to its cable subscribers, then again, you may be right in that "Dish will have the exclusive for quite a while." Not holding my breath on Voom