No surprises in the fact that Hassan Rouhani has blamed Israel for the assassination (see link below)
https://www.bbc.co.uk/news/world-middle-east-55111064
But parts of his announcement which includes wording such as "Iran would retaliate over Mohsen Fakhrizadeh's killing at a time of its choosing."
" would respond in due course" "would not push Iran into making hasty decisions." "In due time, they will answer for this crime"
Leads me to believe they will bide their time and prepare to attack a 'soft' target rather then anything major such as launching missiles into Israel.
Possibly even the bombing of an Israeli embassy.
Whatever it is I am confident Israel will retaliate using superior force.