At this point, no team's win this week means anything in terms of wins in the playoffs (other than helping to get there, which is the important bit in the regular season). I think you're delusion if you think any poster's enthusiasm over beating a very good team means the Packers have already won the superbowl, I don't think anyone has suggested anything like that.
Getting to the playoffs is hard, winning in the playoffs is very hard, winning the superbowl is down right improbable (only 1 out of 32 teams does it every year). I think all of the fans on this site are aware of these realities. However, thus far, the Packers have shown to be a very good team, and in the past 3 weeks have beat 2 of the 3 9-3 teams which they currently share the league's best record with. I would say that being excited about this team's potential is quite reasonable, and you nor I nor anyone else on this site knows what will happen in the playoffs. Its why we watch the games after all.
You can point to loses in the playoffs in previous years, but at this point, only 3 NFC teams that made the playoffs from last year would qualify again this year, and the NY Giants for instance have won 2 superbowls in recent memory stacked between some downright awful seasons, so one year's success or lack thereof generally has very little bearing on the next.
Facts:
1. The year before the Packers won the superbowl, they lost in the first round of the playoffs
2. At least 66% of teams in the NFL finish the season with a loss in the their first game of the playoffs, or worse (not getting to the playoffs at all).
Now, these facts do not mean the Packers will win in the first round of the playoffs (as mentioned above winning any game in the playoffs is very hard), but it does help to keep perspective.