Somaliland missed the bus on recognition in the 20 years between 1991 and 2011. As soon as the TFG ended and a fully recognized FGS was created, the serious hopes for secession came to an end. The most ripe period was the warlord era, between 1991 and 2000, before Cabdiqassim's government. This is when the south was in complete anarchy.
What did the Isaaq do during this period? They had a civil war.
No UN member will ever unilaterally recognize the secession of Isaaq because Somalia is not at war with Somaliland.
The other reason why Isaaq's hopes for secession are growing cold is the shrinking gap in population growth between the Isaaq and Harti. As of 2014, Harti is as large as Isaaq with both at roughly ~2.2-2.3 million. Harti are also growing about 30% faster than Isaaq due to a difference in fertility of more than 2.2 children per woman. Recognizing the secession of the Isaaq would lead to a war that would dwarf the USC-Darod conflict. No one wants another South Sudan.
A simple map of fertility tell you all you need to know about the future likelihood of Isaaq recognition.
View attachment 201076
Let's be honest most of Dhulbahante in Sool & Sanaag might support a united Somalia but they are pragmatic and will work with Somaliland as long as some sub clans support Hargeisa admin.
The only Darood willing to go to war with Hargeisa are found in Buuhoodle & Baran. There will be no large scale war. I think you underestimate how brutal and devastating 2006 war between TFG & ICU actually was.
The most serious war between Isaaq and MJ was in Tukaraq has killed merely 300 people max mind you this conflict was running for over 20 years. 2002, 2004, 2007 & 2018 wars between Somaliland & Puntland casualty was less than 500 people.
2006 war in Mogadishu and subsequent insurgency killed tens of thousands directly and indirectly. The two events are not even comparable.
There is no comparison the only way forward is through a peaceful referendum. Military solution is not an option.
Isaaq & Harti are averse to conflict the IC & most importantly Ethiopia will never allow war to go in northern Somalia.