Streetsblog Chicago has a very informative, detailed report of the changes that will come to Broadway when bike lanes are added. There will be buffered lanes between Wilson and Foster (see below)
and protected lanes between Montrose and Wilson (see below).
The rest of the road will be one wider lane in each direction (rather than the two that exist now) and a center lane for turns that will run the length of the street.
We suggest you read the article for more information. It's very comprehensive. Surprisingly, the city is moving quickly on this project: Street patching begins next week, with painting and restriping following, as weather permits.