Stieg Hedlund (see bio) who worked on both Diablo, Diablo 2 and LOD has posted a blog discussing the future of the ARPG. In the article, he looks back at the early beginnings of the genre including D&D, the CRPGs and JRPGS and where it eventually led to.
In a section called “Send in the Clones” he moves on to the Diablo series and then discusses where he thinks the genre is now heading. Here’s a snip:
Diablo came out at the end of that same year, also picking up the Roguelike trope of the randomized dungeon, which kept the novelty level high. While it was quite successful, and a few clones did appear, it was really the massive success of Diablo II
(D2) that ushered in a flood of them. To me, Diablo proved that we could find an audience for this new game type, and D2 let me explore it much more thoroughly. Many clones, at least initially, were quite literal—wholesale adoption of all the elements in D2, with varying degrees of success.
The full article can be read on Gamasutra.