Free agent De Koning will play his 100th and likely last game for Carlton against Essendon on Thursday night, and is then expected to take up a bumper seven-year deal from St Kilda worth around $1.7 million per year.
Emerging superstar Nasiah Wanganeen-Milera turned his back on huge interest from Port Adelaide and Adelaide to re-sign with the Saints for two years on Monday.
Voss insisted he didn't know what De Koning would do but conceded the only hope Carlton had of him staying was if he had a similar late compulsion to remain with his current teammates.
"I was reading the Nasiah comments and however that's played out behind the scenes, I'm not sure - I think Ross (Lyon) found out five minutes before (it was reported he was staying)," Voss said.
"So sometimes it can happen, as simple as that. But we've maintained all along, it's about what we're doing right now and how he turns up for us.
"And I can't question that, for what he's been like throughout the course of this year.
"So that part's positive, but until you obviously have him signing, you're never too sure what's going to happen next. But we'll let that play out.
"But it shouldn't overshadow the 100 games he's played for the club and the contributions he's made.
"... I guess the only case that we have is that he's got a group that he's growing with, and it's still relatively youngish as a midfield group, and we'd love for him to be a part of that."
In-demand defender Jack Silvagni could also depart, while Carlton will turn their attention to improving their own list.
"We need some depth," Voss said, pointing to the effect of injuries this year.
"That's been a priority for us."
When asked what the Blues, who missed finals, needed, Voss said: "Ideally, clearly, want to bring in some speed and some ball use, and that'd be nice on the edges to be able to bring that.
"Obviously, already got some guys that haven't played a lot of football that we can bring into the team immediately and be a difference for us.
"So in that area is Matt Cottrell, (Jagga) Smith - (Sam) Walsh has come back, you've seen the impact he has."
Football boss Brad Lloyd will depart at season's end and new CEO Graham Wright, who has backed Voss in for 2026, has flagged decisions will soon be made on the Blues' assistant coaches.
"We'll get to the end of the season, we'll take a breath, and then we'll sort of start to make some necessary changes from there," Voss said.
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