The Magpies are committed to signing Armstrong once the window for delisted free agency opens on Friday.
The 24-year-old was expected to join Collingwood as part of the trade that sent Jesse White to the Westpac Centre, but he was eventually withheld from that deal.
Still, it is understood after 15 games in two seasons with the Swans, the former Adelaide midfielder will make his way to a third club through delisted free agency.
As well as White, ruckman Shane Mumford was traded to Greater Western Sydney while Andrejs Everitt made his way to Carlton.
Alex Brown was delisted while Jude Bolton, Martin Mattner and Mitch Morton retired.
The Swans hold selections No.15, No.32, No.35 and No.44 at next month's NAB AFL Draft to be held on the Gold Coast.
Twitter: @AFL_Nathan
