I am now going to build a case that this author intended to refer to two men in the same bed. The basis of my case is that this verse shares parallelism with the next verse which refers to two women grinding together in a field.
Verse 34 (two men in bed):
ὁ - The (article, nominative, singular,
masculine)
εἷς παραλημφθήσεται καὶ - one will be taken
ὁ - The (article, nominative, singular,
masculine)
ἕτερος ἀφεθήσεται - the other will be left
Verse 35 (two women grinding):
ἡ - The (article, nominative, singular,
feminine)
μία παραλημφθήσεται - one will be taken
ἡ - The (article, nominative, singular,
feminine)
δὲ ἑτέρα ἀφεθήσετα - the other will be left
In both verses δύο is used! It is the only the context that helps us determine if δύο is masculine or feminine.
Now on to the translations.
The NRSV leaves the gender neutral in verse 34 ("there will be δύο two in one bed") BUT in verse 35 uses the female gender ("δύο two women grinding together"). Definitely leaving the men in the closet.
The translators of the KJV include the men in bed.
Most amusingly, the Darby Translation apologetically includes the men in bed...
I say to you, In that night there shall be two [men] upon one bed; one shall be seized and the other shall be let go.
This is more fun than Seminary.