I also support this -- time to kill life support on all of these addons. The community expects massive issues when expansions come out, so this will be per usual. Elkano, I was strongly considering tackling an Ace3 replacement for EBB next... but I won't if you're really planning on doing it. :)
4.0 will break most addons anyway, and the mechanics of the game are changing enough that mods like Pally Power will need somes sort of update. Although, it has been rather amusing seeing the creative ways Ace2 breaks with every patch.
Will it really? I hate when people make such broad statements about addon breakage, especially when addons haven't even been enabled in beta yet.
Game mechanics are changing enough that the majority of addons based on game mechanics have to be updated. It looks like the old power events are being removed, so that will break UFs. Talent APIs are changing enough that anything that relies on them will break. Guild APIs will probably also change enough, but that remains to be seen. Spell book and the profession page too, and the character pages.
Last I looked the arena page is also being updated.
And that's early into beta, without addons being enabled yet or all the changes being fully implemented. Chat addons might escape without horribly dying, but I wouldn't be surprised to the majority need updates.
This isn't counting the dinky 50 line type of addons, because those don't use Ace2 anyway... and the ones that do are cause the authors have no idea what they are doing.
Anyhow, the alpha builds didnt have many UI changes, it basically only started to be bigger diffs since they disabled addons. We'll just have to wait and see until they are enabled again.
On that note, i haven't seen many changes to the big parts that addons use, like templates, secure headers, and all that. Obviously talent addons and everything working with the guild pane or spellbook will need to be fixed/rewritten, but other then that .. not much yet.