Your reference says that there will be continued exploration, but doesn't mention another actual fly-by. Funding beyond 2021 isn't confirmed, and even if they top up the funding, they can't top up the manoeuvring fuel.
"And we hope to hunt down one more KBO — one more Kuiper Belt object — and make an even more distant flyby in the 2020s," Stern added [...] New Horizons [...] has enough juice [...] to keep the power on through the mid to late 2030s, he said.”