But actual confirmation of the news, for example in the form of a press release, is in fact not expected this weekend at Monza.
"There will be no announcement at Monza with regards to the drivers," Mattiacci is quoted by Italy's Autosprint, "because there's nothing to announce."
He says that is because Alonso and Raikkonen are already under contract for 2015.
Technically, that's true. But Germany's Auto Motor und Sport claims that September 1 could change everything.
Correspondent Michael Schmidt cited 'internal sources' as confirming that Alonso's contract contains a clause that opens the potential exit to the Spaniard if he is not within 25 points of the championship leader on September 1.
Prior to Monza, Alonso is actually closer to 100 points behind Mercedes' Nico Rosberg.
It doesn't mean Alonso will jump at the chance to leave, but Britain's Telegraph newspaper reports that - despite their history - McLaren chief Ron Dennis has made an astonishing offer of $32 million per year to Alonso.
The report said Dennis, although having spectacularly fallen out with Alonso in 2007, "has spoken with Alonso" about the Spaniard's return to Woking to head the new Honda-powered project.
Alonso, however, might be alarmed by the latest rumours emerging from Japan.
The rumours suggest Honda, returning to F1 in 2015 after a six-year absence, is currently "far behind the performances" achieved by leading engine supplier Mercedes as it works on its all-new turbo V6 'power unit' for McLaren.