Future replacement is not yet known, but whoever comes will not have an easy job to return Microsoft to the level from the '90s when they were the undisputed ruler of the IT market. However since Ballmer became chief things are quite the opposite According to an official statement, the hunt for a new director is just starting, and the transition will be run by a special committee that will oversee the company's work in the period between the two directors.
What investors think about Ballmer leaving the company's leadership showed at the stock exchanges where prices of Microsoft soared by 9% immediately after the announcement of this news. Interestingly, the financials indicate that Ballmer was not a bad manager - during his reign the annual revenues of the company jumped from 23 to 70 billion dollars. Nonetheless, the company's share price stagnate, and by Forbes he was named the worst CEO of all large U.S. companies that are on the stock market.
[Ed - This has been a long time coming, but our guess is that the failure of Windows 8 and Windows RT (and the monet lost on the Surface RT) had a big impact. Microsoft under Ballmer had no real direction which contributed to many of the problems that Microsoft has had in the recent past. Ballmer's push to become more and more like Apple while branching out into cloud services was just too much for their customer base. We hope that Microsoft returns to their core strengths and drops the attempt to become like Apple and Google. If they can do that, and quickly, they might be able to pull things out of their current state...]