In English, it's hard to avoid "we shall return" after General McAuthur's famous remark in WW II. In fact, hardcore traditional grammarians would insist that we should use "shall" and not "will" as the Duolinguo translation demands.
Am I the only one who can't hear the "L" in voltar? I've gotten used to this little quirk, but I wonder what it would sound like to hear both votar and voltar pronounced together.
In Brazilian Portuguese, «l»s will commonly be pronounced as [w] in IPA. However, the vowel quality of the two verbs maintain an important distinction: the «o» in «voltar» sounds like "aw" in the American English "law" or [ɔ] in IPA (even though it kinda sounds like [o] here), while the «o» in «votar» sounds like the "oo" in "too" or [u].
In correct English usage "I shall" and "We shall" are, respectively, the first person singular and plural of the future tense of the verb "to be". The use of "will" instead of "shall" in these cases either makes the verb into the subjunctive or is purely an example of lazy speech/writing.