I contacted Guest Communications -- the response: "The Front of Line pass will be available for purchase when the Wizarding World of Harry Potter™ opens in April and will continue to offer the same one-time use front of line benefits as it does today. Please keep in mind the Front of Line ticket is subject restrictions and availability."
I haven't heard yet if a return ticket into Hogsmeade will be required for Front of Line ticketholders at times when the land is full. Perhaps they would at least be granted to go to the front of the Hogsmeade queue for a given return time. We'll see.
Another question, will Forbidden Journey front of line ticket holders still see the castle on the way in, or will they enter through the single line queue (or similar) and miss the queue features? I've asked the question -- we'll see if they know.