Maybe I'm wrong, but I never got even the slightest hint that SE intended to release the second or third waves of Alexander HM and Savage separately. The delay this time around, or at least a lot of it, was because of the expansion and not wanting people to feel rushed to complete it (potentially missing out on at least 1 if not multiple weeks of lock outs).

Maybe they'll release HM at 3.2 and Savage at 3.21 next time, but I think this would be a mistake. For 3.0 people needed to gain 10 levels and roughly 40 ilvls to catch up to Alexander HM (really dislike the lowest tier of things being labeled 'Hard' btw), never mind the massive amount of story that took place and just getting acclimated to 3.0. For 3.2, people will be geared up, likely in full i210, while Alexander HM will probably only require i180-i190 (almost certainly not higher level gear than the previous iteration) and Savage shouldn't require anything more than i200-i210 (again, no more than the previous tier) and people will be ready to start immediately.

No, I think the tiered roll out was entirely to do with the expansion and won't be repeated in further patches since the only purpose it could serve is if they want Alexander Savage to require better gear than you can obtain in the previous version of Alexander Savage (or upgraded 'capped' tome gear), thus requiring a few repeated completions of Alexander HM + new tome gear even to get in. Those sort of strict ilvl requirements haven't been seen before (usually they're fairly loose) so a delayed roll out shouldn't serve any purpose at all.