For those that don't have an interest in contemporary Italian cinema, it should be noted that the Italian film industry is notoriously insular. Meaning not only is it not surprising that most Americans are only hearing of this franchise now that Travis Bickle has joined the cast of the third entry, but also that neither Manuale D'Amore 3 nor its two predecessors will ever likely be released States-side.
This means that producers and studio executives consider these film's style of comedy to be too provincial, whatever that means, and hence just don't want to take a chance on a potentially receptive new market here in America. Also De Niro will speak Italian for the role naturally, as pretty much everything in English language is dubbed into Italian in Italy, save for the junky reality shows on MTV Italia (I don't know why this is but it's very strange to watch Next in English with Italian subtitles).
That part of Variety's announcement is to be expected. What's interesting is the idea that De Niro is involved in the project. This is the second role after the recent remake of Giuseppe Tornatore's Everybody's Fine, also based on an Italian romantic comedy, where De Niro plays a lonely old widower who presumably takes a chance on love in his old age. Obviously I can't generalize and say that perhaps old man De Niro has accepted his age and gotten tired of macho roles--the man is clearly holding a gun in the Machete trailer but then again, though he looks like he's playing a politician that curses more often than he actually gets his hands dirty. But maybe De Niro is becoming a softy in his old age. Anyone see and strongly like/dislike the American remake of Everybody's Fine? Sam Rockwell was in it, fer cripes sake!