Ben Smith at Politico reports that Obama and Clinton will be in Florida on Wednesday.
I somehow doubt it's going to be a joint rally. It likely will be two separate rallies, with Obama in his general election mode, and Clinton in her primary mode, yelling about how FL voters were disenfranchised and how the delegates MUST be seated. It's certainly going to be something for the media to focus on. Hence her following Obama to Florida.
And I think it's to blunt off any impact he might have from a new surprise endorsement there.
EDIT: Mark Halperin at Time's The Page reports that they might be sharing the stage together.