Yesterday, most people thought that there will be no war with Iran in 2020. I think now that some of those that voted NO would probably change their mind after the latest escalation.
Qasem Soleimani, the commander of an elite unit of the Iranian Revolutionary Guards - The Quds Force, was the second most influential figure in Iran, only Ayatollah Ali Khamenei is considered more powerful.
The guy's been a rock star amongst the Shia Muslims in the region and instrumental in organizing pro-Iranian forces in their fight against the Sunni extremists (ISIS/al-Nusra/...). Even if Iran didn't promise to avenge his death, even if the official Teheran is against any such action (they are not), I don't think they could prevent it.
There are many armed men across the region for whom Soleimani was a hero and now a martyr. The rise in the number of attacks, both coordinated and organized by Iran and the attacks by the Soleimani loyalists against the US/Western personnel and interests in the region are unavoidable now.
We all know that Trump will respond to any such attack and we are on the way to a proper war.