Hopefully, we will not set off a firestorm of controversy. Hopefully, we will use no more cliches in this piece.
What kind of a grammar expert starts a sentence with "hopefully"? The sort of grammarian who understands that sentence adverbs are common in American English and that the prohibition against using "hopefully" as a sentence adverb came about in the second half of the twentieth century, for no very clear reason.
Adverbs such as "thankfully," "frankly," "actually," and the like are quite common at the beginning of sentences. They modify not just the verb in the sentence, but the sentence as a whole. Rhett Butler's "Frankly, my dear, I don't give a damn" raised no eyebrows for its first word, although a few may have lifted over the last one. "Frankly" was understood without censure.
Yet, since the mid-1960s, American grammar teachers went on a crusade against "hopefully," seeing it perhaps as an example of sloppy writing. The prohibition against its use has long been yet another shibboleth of grammar. My theory is that many of the less well-founded usage directives of that time were a prescriptive reaction to the permissiveness of 60s culture, sorts of lines in the sand that those protective of order drew to maintain authority of sorts, of some sort, of any sort.
But in the sense that "hopefully" means "it is to be hoped that," it makes perfect sense to use it as a sentence adverb. Adverbs modify much more than verbs, of course, as anyone can see who takes a second or two to look at English and how it is used.
Of course, once again one has to know to whom one is speaking. If the audience is your boss, who has persinickety and unfounded grammar "rules" and also pays your salary, hopefully you won't use this construction. Or, it is even more fervently to be hoped that one can use any of dozens of modern grammar arguments to convince him or her otherwise.