Colony Square's major redevelopment could include a new tower. But whether that will be apartments, hotel or office is still up in the air.

North American Properties' John Kelley said the developer — known for its haute Avalon mixed-use project in Alpharetta and turning around Atlantic Station before selling it in 2015 — is eyeing a new building on the corner of 15th and Peachtree streets that would at least have ground-floor retail.

It would also be among the last phases of Colony Square's transformation, but is set for a 2020 completion, Kelley said. “The size will really be determined by the use,” he said.

Kelley is among the panelists at Bisnow's Construction & Development event next Wednesday at the W Hotel Midtown. His firm presented its latest retail renovation plans to the Midtown Alliance last night, plans that will includes new, two-story storefronts to the 100 and 400 buildings, removing the roof over Colony Square's mall, and moving retail forward “to better engage people on the street,” Kelley said. North American also plans to scrap the motor court off Peachtree Street and move it to the back of the property, he said.