Dempster isn't going anywhere. There's no denying that he's sucked the last month, however, the Cubs as a whole have sucked as well. Dempster hasn't had much of a chance to pitch these days, so it's no wonder he's got no control when a save situation very rarely occurs.
Howry is next in line, without a doubt. It just won't be happening unless Dempster is hiding an injury or something.