It's baseball. Sometimes bad teams win games. There are some reasons for concern already (the IL list, the teetering bullpen, the workload on Ashby and Uribe, the drop in bat speed from several players that Matt wrote about), but you can't reasonably demand/assume a sweep against any team. if they drop 2 or get swept then that will likely be because those warning signs noted above continue to be a problem.
I know it's worrying season because this is, or is rapidly nearing, the time of year when things to to hell for the Brewers since 2007 or so, but if they go .500 the rest of the season they set a franchise record for wins and the Cubs would have to finish the season on a 14 game win streak to win the division. Let's try to enjoy the last 2 weeks of the regular season! Plenty of time to be miserable when the playoffs get here and they're playing teams with $200-300 million on the payroll every series. :)