Good question. As we learned from Mission Impossible, it's only a 16th note, and the direction is poco allargando, not molto allargando (slow down a little bit, not a lot). So it's at least indulgent, if not against the composer's wishes, to hold that note forever. Then again, the effect is thrilling, and it's one of the most famous and indulgent moments in opera, so if you got, flaunt it...(maybe purists would disagree).
An important point about the compilation that some people might not realize is that there are three categories going on here:
1. Trained opera singers who are performing in a concert hall (although we might be hearing a different audio mix as it was recorded, the live audience heard this without amplification)
2. Pop singers who are amplified because it's not an acoustical hall but also because their voices would never carry over an orchestra anyway
3. Trained opera singers who are amplified because they are singing in a huge amphitheater (like the Three Tenors at the end of the video, or Pavarotti in the Boston hatch shell)
Because a lot of people don't make it to an actual opera, they take for granted that everything we see on TV is miked and remixed and amplified. But "opera is hard" because what separates opera from musical theater is that your voice needs to carry naturally.