Trumbull is way too close to Milford so highly unlikely. Will probably be Danbury.
That said one along the merritt parkway would be nice as opposed to the milford one on 95
Look at how close Greenwich/Darien (and even Tarrytown, NY) are. They all serve different major routes, Greenwich on the Merritt Parkway, Darien on 95 and Tarrytown serves 287/87/9/9a and the Saw Mill Parkway. A Trumbull site, in addition to the Milford Mall site at or near the Trumbull Mall makes sense because they would both serve different routes.
Also -- Danbury Fair Mall would be an excellent location. I heard Tesla has actively been looking in the Danbury area for some time now. Across the street in the shopping center where Whole Foods and Panera are would be a great as well. I know this Whole Foods has a couple level 2 chargers also, so not sure if the property owner would be interested.
Remember -- at the time Tesla was looking into the West Hartford area, the owners of West Farms mall did not agree a Supercharger would be beneficial to their businesses. So, Tesla built one across the street at the Corbin's Corner shopping center. Danbury has many other options for locations as well.
They can also look a few miles down the road -- Brookfield, CT (just east of Danbury) also has many shopping centers where a Supercharger could be built. Also, exit 19 of 84 in Brewster, NY, there is a shopping center with an Applebees, Dunkin' Donuts, Kohls, Home Depot, and a few other shops and restaurants. While Danbury/Brookfield would serve mostly people heading west on 84 to 684, Brewster, NY could serve people heading east on 84 to 684.