Your right in saying that the current leadership of the Night Elves do not recognise the current armistice, and it is yet another example of emotions getting in the way of pragmatism where the option for a peaceful settlement is potentially on the table which would prevent further casualties.
Although, that said i’m not going to dismiss their reasons for disregarding the ceasefire are not without merit due to atrocities inflicted upon them. Even if they were carried out under the orders of Sylvanas, ordinary members of the Horde military force present during the War of Thorns did participate in the mass slaughter of civilians unprovoked. By all accounts a war crime which has yet to been answered for in kind or otherwise.
Neither is it being suggested that the Horde are themselves planning on taking advantage of a wounded Night Elf faction nor is the possibility of marching on Hyjal being pandered a plausible eventuality. That would involve besieging territory deep within Night Elven lands most of which is impassible terrain of what is essentially a natural mountain fortress. Not to mention the logistical nightmare of securing supply lines up there and protecting them throughout hostile territory as you’ve touched upon. It would be a fools errand to do so or even consider such an attempt with a depleted force. There numbers required to carry out such a campaign are simply not there and would be, as you’ve rightly stated, worn down via attrition before they even got there in any meaningful capacity to carry out an effective assault.
With the new Horde Council acting as the governing body they a more so in a period of self reflection and reconciliation internally and, by extension with the Alliance too in attempt to alleviate current tensions. I don’t think either side (barring the Nights Elves & Worgen) are at this point in time looking to pick a fight and stoke further conflict and strife over the pretext of revenge.
What is essentially being requested here is that existing Horde claims within the region east of the Falfarren River are recognised for what they currently are. In fact as previously mentioned in such a proposal the Horde would be withdrawing from all their holds West of it, ceding a substantial amount of ground in the process. It could even be considered a form of reparations in the form of restitution.
In addition, I don’t think it would be to much of stretch to suggest that if other members of the Alliance were able to secure reciprocal recognition in return, for other disputed lands or concessions from the Horde elsewhere (especially those within the Eastern Kingdoms), that they may pressure the Kaldorei into accepting such terms, and if failing that withdrawing their support for them in some manner in protest.
WARNING! Shadowlands Spoiler
Turalyon himself now acting regent come SL has already expressed an interest in securing lands previously held by the old Alliance of Lordaeron. So i do not believe such a potential scenario is totally out of the question.
“Reclaiming Stromgarde was a good first step. Perhaps there are other holdings of the old Alliance that could be secured.”
It would work well to serve as a plot device to stoke further internal tensions within the Alliance which itself is long overdue.
I’d be curious to see how the chips would fall and which sides individual Alliance faction leaders would take if such an event were to occur in the near future.
Another point of consideration is although, Garrosh may no longer be held in high regard by the Orcs, his father Grommash still is.
Demonfall canyon situated within the south eastern corner of Ashenvale could also be considered sacred to the Orcs if not a place of pilgrimage. This being the site where they were liberated from the demonic taint of Mannoroth and ultimately freed from the shackles of the Legion. It’s a bit of a stretch i know but, it does help to counter claim previous statements about the land itself being sacred to just the Night Elves themselves.
It may have been the Kaldorei’s charge during the Long Vigil to defend these lands and Nordrassil but, when the time came during the events of WC3 upon the return of the Legion lead by Archimonde, many races including the Orcs also gave their lives in defence of the World Tree. Made possible in a large part due to Grommash’s martyrdom not just for his race but also Azeroth as a result of his personal sacrifice, regardless if he saw it as such at the time.