I don't think so. I mean, I agree that it's tough to unseat an incumbent, but special elections are turnout elections and all the emotion was on the Dem side of things, all the money, all the issues (the GOP's best issue was a response to the phony issue).
Next time around the emotion won't quite be there, not at that level, because it will have been a year and the world will not have come to an end. The turnout will be more representative of the entire population (if Dane is mobilized to vote so will other areas). That's why it's always important to get the big "nasty" things done in the first few months, then the general public has time to realize it didn't affect them all that much. A lot of the emotion then dissipates.
AP is now showing Milwaukee as being all in (all precincts reporting), with no change in the vote totals. We’re now down to one precinct (Lake Mills) in Jefferson County, one that cast over 2,300 votes for Governor last November. Given the turnout numbers, it’s likely they cast 1,500 or so votes yesterday.
They were fairly narrowly for Walker last time so I don’t think Prosser is going to win big there (for instance, Obama had about a 15-point margin in that precinct in 2008 even though the county as a whole was split between Obama and McCain). Close the 224-vote gap some, but not eliminate it.