A是最有可能的出版社

A is the most possible publishing company
A is the most possibly a publishing company

A is the most likely publishing house for/to

A is most likely to be a publishing house

A是最有可能的出版社
A is the most likely publishing house for/to

这里需补充点内容，解释最有可能的事情，例如获奖
则可表示为A is the most likely publishing house to win the award.

A最有可能是出版社
A is most likely to be a publishing house

解释

出版社：publishing house 或者press
这种场合下，要用likely，不用possible