In one of the standard "MAYWEATHER-PACQUIAO!" bits where he was asked about that fight, Bob Arum also made note this week that Top Rank and Manny Pacquiao have a rematch clause in the event that Chris Algieri scores the upset on Pacquiao on November 22, so the idea of Algieri beating Pacquiao and fighting Mayweather is likely not on the table.
On Mayweather-Pacquiao, Arum said that Mayweather is reluctant to fight Pacquiao, and that, "If people don't see that by now, they're never gonna see it."
What people are mostly upset about is that what they're never gonna see is the actual fight, and we've lost the time when it would have been the best it could have been. It remains a must-see event, of course, but it's not the fight it was in 2009-11, either.
Of course, the real reluctance likely comes from Mayweather not wanting to work with Arum, since he's also not fought anyone else under the Top Rank banner since he left Arum's stable many years ago to secure a fight with Oscar De La Hoya in 2007. But then that doesn't go along with the whole "Mayweather is afraid of Pacquiao" routine.
Most of you are quite well aware that this fight hasn't happened for any number of reasons, and that neither side really deserves to escape blame, and that really, end of the day, everyone kinda sucks for this fight never happening. It could have, but it didn't, and it almost certainly won't.
As for Algieri, the rematch clause is obviously no surprise. Champions generally do have rematch clauses, anyway, and it's a protective measure for Team Pacquiao in case he loses, or if there's some goofy reason he loses, or whatever.