Several sides are believed to have shown reported interest in McStay's services, with the Magpies being among the clubs linked to the Lions forward.
A Victorian native, McStay could be persuaded to return to his home state, with enticing offers from rival clubs understood to be on the table for the 26-year-old.
A rumoured five-year, $3 million offer had also been floated for McStay, with Collingwood emerging as the high-priced bidder, according to The Age.
The publication have reported that the Pies are the front-runners for McStay, with their offer likely to blow the Lions out of the water financially.
Brisbane are also believed to have tabled a five-year deal after strengthening their negotiations, however their sum falls close to $100,000 shorter than that of Collingwood's per year.
The Magpies have struggled to recruit or develop a dominant tall forward across the past decade, having seen the likes of smaller forwards Brody Mihocek, Jamie Elliott, Will Hoskin-Elliott and Alex Fasolo share their past seven goalkicking awards.
Mihocek has shown the ability to lead Collingwood's young attack, but hasn't done so with a complimenting partner in crime.
It is understood that Cox is expected to trigger an extension clause in his contract for the 2023 season, while Cameron is reportedly progressing through talks on a new deal at the AIA Centre.
The Magpies will also be wary of Jordan De Goey's future, with the club having reportedly pulled a $800,000-per-season contract from negotiations following the midfielder's recent Bali trip saga.
Should De Goey turn down the club's next offer and exercise his rights as a free agent, the Magpies could lose draft compensation should they land a sizeable deal for McStay.
That could see the Lions and Magpies come to the trade table and work through negotiations in swapping assets as opposed to seeing McStay depart as a free agent in a move similar to that of Richmond and North Melbourne last year.
McStay has played 150 games for the Lions since making his debut in 2014, sharing his time in defence throughout the early seasons of his career.
Brisbane will travel to Melbourne this week to face the Demons at the MCG on Thursday night, with the top-of-the-table clash to commence at 7:20pm (AEST).