Has anyone talked about how/if Universal will change it's admission policies or costs IF the train station actually connects from US to HP in IOA? Or are they just expanding HP over that far (i.e. not actually part of US) and the train will fall under the admission price for IOA? That brings me to another thought. IF the train station really connects, then do you think there's a future possibility of only having only one admission price that would cover both parks? Do you think they would ever do away with the "One Park" ticket completely?
First.... If they are taking the Amity Area and turning it into Harry Potter Phase 2 as the rumors are suggesting, It DEFINITELY will be part of the US park and not IOA. Besides the fact that creating a bottleneck in the Hogwarts Express as the only way to access the "distant section" of IOA being incredibly unworkable and stupid.... If they wanted to keep Harry Potter exclusively part of IOA, they could've annexed the remainder of the Lost Continent as people originally expected them too. The primary reason for putting it into the old Amity/Jaws plot would be to help drive guests into US since it hasn't seen the same attendance jumps as IOA. [in turn meaning more multipark and multiday ticket sales].
Second... I kind of doubt they'd get rid of one-park tickets entirely... If nothing more because of the way one day tickets are priced identically between most of the area theme parks.
What i could see as more likely would be the potential elimination of multi-day one-park tickets. Here's the logic behind my thoughts.
Currently every park in the area has their one-day one-park tickets priced around $89. Even (and especially) Disney. The 2 park one-day tickets are a small surcharge above that base cost. Therefore, It would put Universal at a slight disadvantage marketing wise to have their one-day tickets cost more than either Sea World or Disney One-day tickets.... and the accountants would never let them lose out on the extra money they currently make off the 2-day one-park tickets.
What might be more likely to happen to try and avoid guest confusion or hassles on a ticket check at the Hogwarts Express would be to look at Disney's ticket history. Prior to the MYW ticket introduction, All Disney Multiday tickets were Park-Hopper Tickets. You could purchase a one-day one-park ticket, or you could purchase a world passport which included access to multiple parks over multiple days. Universal could very easily adopt this older ticketing policy and thereby tell guests You can either access 1 park on one day, Or all the parks over multiple days.
At the Hogwarts stations, it would then simplify the ticket checks since if a customer has a multiday ticket, then they get to ride the express. If they only have a one day ticket, they'd need to upgrade to a multiday ticket.
The other option might be to allow guests at the Hogwarts station with a one-day ticket to purchase a "Hogwarts Express ticket" that just happens to cost the same amount as the park-hopper surcharge for existing one-day tickets.
This is obviously all conjecture on my part with nothing concrete to base it on. I do however expect some changes to happen in the ticket offerings if nothing more to try and help lessen customer confusion, ticket checking delays at the train stations, and potential unhappy guests who don't seem to understand why they can't ride the attraction with their one-park tickets.