So, in a nutshell,
1. Several fans of existing Mattel DC Universe lines are looking forward to them continuing. DCUC or its replacement. Young Justice. JLU.
2. Fans of the 3.75" scale wish that Mattel would put a better effort into the 3.75" scale or that Hasbro would get the license so the fans could get 3.75" DC comics product comparable to Hasbro's Star Wars and Marvel figures in the 3.75" scale. They did like Mattel's efforts in the Infinite Heroes line.
IMO, the problem is that JLU succeeded too well. Infinite Heroes appears to have been intended to replace JLU, but then ended up on shelves next to it. People did not switch. (To me, the scales was too close for me to rebuy the same characters. My investment in JLU was too large to switch.) Young Justice is now Mattel's main line in the roughly 4" scale. We also have Action League.
It is clear that there IS a demand for DC product in the 3.75" scale. So, Mattel, take this info and run with it.
Did I miss anything?
I disagree with this in part. I do not believe DCIH was meant to replace JLU. I believe JLU was for the TV show and DCIH was for the books, and to compete directly with MU. Mattel constantly talks about dollars allotted to go where and I think that became a problem, they just did not have the dollars to allot to DCIH to make it competetive with MU. ( Of course I no longer give much credibility to those types of answers from Mattel anyway, but that is another discussion. Taking what has been said at face value...) If both Hasbro and Mattel are allotting the same amount of dollars to their respective licenses, consider; Mattel is producing 3 different scale lines that are competing for those dollars, Hasbro just one. Who will end up with the higher quality product. Hasbro has the better line because they invested more in it. Another problem with DCIH was the shear number of figures being released in the time span. It was impossible to keep up, when you could find them. Hasbro has done a much better job at spacing out the releases so as not to shock the limited budgets of it's customer base.
People who like DCIH, like me, do so because it is the best there is, so far. The last time we had these characters in this scale was Mego, and these just look so much better that those, thanks to time and technology. The problem is Mattel. They mismanaged the license from day one, and got really lucky with JLU and DCUC, but DCIH should have been better, both in appearance and in how it was handled. Now Mattel is using that failure as an excuse not to resurrect the scale, but for that excuse to work, it has to be anyone else's fault but theirs, because if it was their fault, they could fix it, most likely by correctly firing someone who is scratching and clawing to hold onto a cushy job they can't do and don't deserve, and we end up suffering for it.