In The Elements of Style, my bible of writing, we can find the following passage about the word "hopefully":
This once-useful adverb meaning "with hope" has been distorted and is now widely used to mean "I hope" or "it is to be hoped." Such use is not merely wrong, it is silly. To say, "Hopefully I'll leave on the noon plane" is to talk nonsense. Do you mean you'll leave on the noon plane in a hopeful frame of mind? Or do you mean you hope you'll leave on the noon plane. Whichever you mean, you haven't said it clearly. Although the word in its new, free-floating capacity may be pleasurable and even useful to many, it offends the ear of many others, who do not like to see words dulled or eroded, particularly when the erosion leads to ambiguity, softness, or nonsense.
I am using the third edition, which was published in 1979. And in the first edition of the Harper Dictionary of Contemporary Usage, which was published in 1975, the following question was put to the panel of consultants, which had more than 130 members:
The adverb "hopefully" is often heard in the sense of "we hope" in such sentences as "Hopefully, the war will soon be ended." Would you accept this formulation?
Here was the result:
In speech Yes: 42% No: 58%
In writing Yes: 24% No: 76%
Twenty years later, in the New Fowler's Modern English Usage, the use of "hopefully" in sentences like "Hopefully, one day we will not argue any more about the use of the word 'hopefully'" is still referred to as "the disputed modern usage". As the book says, "[t]he unofficial war rumbles on."
But I think if we now had a panel of consultants like the one mentioned above, their answers to the question about "hopefully" would probably lean more towards "Yes".