The reapers are either destroyed or rendered harmless in 3 of the 4 endings for ME3. Not sure what the hangup is over them nor why you would imply that only the Reapers could be a threat to humanity. Very narrow way of thinking there.
BTW, Exploration is awesome! Shame on you.
I'm glad that Columbus and other explorers didn't have your attitude
OK guys, I'm coming around to the whole 'Yay Exploration!' vibe, it was 6am here in NZ and I stayed up all night to see the footage then the 2185 'Not-Reaper-Related' bombshell must have broken my sense of adventure for a second there lol.
Since we've identified 'Golden Planets' and such, I'm thinking this recon and possible return route back to the Milky Way with resources could make sense then, especially if they're counting on in 600 years, tech to have advanced sufficiently in this galaxy to make that happen.
I've also come to think that
someone in the expedition group, either in high management or ownership, knows all about the Reaper threat, and unbeknownst to the crew, this is the true reason for their departure date being right after the Sovereign attack and during the Collector threat in ME2.
I'm starting to get on board here Columbus, let's sail to the new world and bring back riches! (also my head canon is legit now, I just had to sort that out first, lol).