Registered here just to tell my opinion 
I’m mostly ok with changes for lore continuity as long as they don’t affect the original story or gameplay in any way. I don’t mind making minor tweaks in map design to be more in line with WoW or maybe even adding a bit more minor character dialogues, but all the original quest objectives (and gameplay behind them) and existing dialogues must remain the same unless it’s a direct retcon (which seems to be the case so far, and it’s good). And if it is a retcon, they should try to work around it or soften it to still make it as close to the original as possible.
I really love suggestions that @Akhan made, especially his Thal’dranath idea. It will make the tileset change unnecessary (as Thal’dranath was probably raised alongside the broken shore and simply didn’t exist 20 years before being discovered by Maiev). It will allow leaving the mission pretty much unchanged, as we don’t visit this location in WoW anyway, and the Moonguard, the Highmountain tauren, the Nightfallen and other mainland Broken Isles folk could be reluctand to explore this island throughout 20 years since the Tomb of Sargeras was raised, due to 1) the scary tomb emanating demonic energies and 2) the never-ending battle of orcish undead. The only issue that will be difficult to address is the Suramar city dome that is literally right next to the tomb, but I’m sure the developers will figure something out.
So yeah, the Horde didn’t know about the isles until Gul’dan went there, the Alliance didn’t know about the isles until Illidan and Maiev went there (note that both discoveries were made thanks to hints from the Burning Legion), and the reason why nobody ever found these isles throughout previous 10 000 years is that the isles are very close to the Maelstrom, ant the sailors simply stayed away from it out of fear.
The last part may or may not be retconned, but I believe it wasn’t as the scale and the location of any geographic objects on WoW map is not an accurate representation of actual Azeroth. It actually gives WC III reforged developers a lot of freedom, as a lot of differences in all three games can be explained away by all of them being canon thanks to scale inaccuracies. So the Stratholme zoo wasn’t retconned, it simply wasn’t featured in the new version.
What personally concerns me is that new WoW lore seems to retcon the existance of the entire class of WCIII heroes - the demon hunters. The new lore seems to imply that all demon hunters are Illidan followers, and they appeared no sooner than TFT events and have no ties with the night elves remaining on Azeroth (until WoW Legion that is). I wonder how reforged will handle that issue, even if it’s not directly relevant to the campaign. Maybe the implication is that all non-campaign maps with night elves happen during or after BfA? That would be weird but marginally acceptable. Or maybe lore-wise only the most fanatical followers of Illidan were imprisoned after BC, while ones that weren’t fanatical left Illidan to remain in Azeroth shortly after TFT and were begrugingly accepted back into night elf society.