Hello Moira! Welcome back to the Disney Parks Moms Panel.
The first restaurant I took my wife (then girlfriend) to on our first trip to Walt Disney World Resort was the
Portobello Country Italian Trattoria. It holds a special place in our hearts.
When I saw your inquiry, I was concerned that this was a sign of the end of Portobello, and that it was slated to close after that date. However, I quick call made me breathe a little easier as the unofficial response I received was that the Portobello Country Italian Trattoria may be scheduled for construction or refurbishment at that time and as such, was not taking any advanced dining reservations.
You should try to make reservations closer to your travel dates. If the plans for refurbishment or construction change (as they do from time to time), then advanced dining reservations may become available.
As an alternative to Portobello Country Italian Trattoria, I suggest:
You can always cancel your new reservations if the construction or refurbishment plans for Portobello Country Italian Trattoria change in your favor.
Wherever you choose to eat at Disney Springs, it's a veritable feast for the senses!
Have a Magical Vacation!