"End of an Era" was less about the Undertakers streak and more about putting the Attitude Era of wrestling to bed with a (debatably) proper send-off. The undertones of the match were that guys like HHH and Undertaker did (and can mostly, still do) things that this latest crop of "Superstars" can't, won't, or aren't allowed to. Things like true Hell in a Cell confrontations that expound violence, sledgehammers being used prominently, and knockdown drag-out grueling matches where the spots that risk health and well-being far outway the more calculated stuff that, above all else, attempt to play it as safe as possible.
Don't get me wrong... that's not to say that todays WWE competitors don't put their bodies on the line everytime they go out to the ring or that they don't pull off good/great matches. It's just a completely different landscape now. Concussions are a dirty word in wrestling (even if they're not legit), as are headshots in general and even blood in a WWE wrestling match. Certain moves (piledriver variants, etc.) and more mature and over the top storylines have given way to the "social media" era where Facebook and Twitter are heavily integrated into the product.
To that degree, Trips vs. Taker at WM was indeed the "End of an Era." A close to what wrestling used to be, particularly in the mid-late 90's. In short, it was Vince/WWE's attempt to get those of us who yearn for those days gone by to finally call it a day and accept the WWE product as it is now.
Honestly, I think it was at least partially successful. On the other hand, WWE '13 will have a full-blown "Attitude Era" mode and CM Punk's pipebomb from last summer was linked in the press release as being synonomous to that time in wrestling history.
Couple that with yet another ECW DVD release and perhaps there is still some "Attitude" left proceeding the Trips/Taker "End of an Era" match.