According to some of the posts at http://www.apartmentratings.com/rate/IL-Chicago-Millenium-Park-Plaza.html, a new high rise is planned for the space between Millennium Park Plaza and Randolph, where La Strada is currently located. I wouldn’t have thought there is enough space there to contruct a new high rise. Units facing south will lose their view of the park.

I found a Sun-Time article discussing the development –
http://www.findarticles.com/p/articles/mi_qn4155/is_20060801/ai_n16652488
“Bob O’Neill, president of the Grant Park Advisory Council, said the quality of the architecture will make or break the project. “Millions of people will be looking up at that building. It should be close to a work of art.”

It would join a vista from the park that includes the One and Two Prudential Plaza buildings, Aon Center and the Blue Cross and Blue Shield Building that is due for a 24-story addition. A block to the north are two development sites: one due to get a 65-story Mandarin Oriental hotel and another that’s a possible expansion site for the Fairmont Hotel. “