1
general::
Phrase(s): in all probability
very likely; almost certainly. • He’ll be here on time in all probability. • In all probability, they’ll finish the work today.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, in all likelihood. Most likely, almost certainly. For example, In all probability we'll be home for Christmas. This expression was first recorded in 1617, the variant in 1664.
American Heritage Idioms