Back in 2017 Nintendo of America president Reggie Fils-Aime noted that 2018 wasn't the end for the 3DS, explaining that the company was going to "continue to bring new content...to keep [the] device vibrant and keep it going well into 2018 and beyond." Given the 3DS' success that statement made sense, but with recent sharp drops in hardware sales and the Switch/mobile eclipsing much of that market, Nintendo's tune has changed over time.
Speaking at a recent financial briefing, current Nintendo president Shuntaro Furukawa addressed the 3DS market, noting that it has "contracted faster than we anticipated." He re-iterates that many 3DS owners are buying it as their "first game system," given its "desirable price point," and once again says that there is room for both the 3DS and Switch in the current market.
That said, Furukawa is also going to keep pushing the concept of "multiple Switch units per household," a line that the company started using throughout 2018. He notes that the mentality of "having my own Nintendo Switch console" is a goal to strive for.
So yeah, Nintendo has acknowledged the slump but the 3DS still isn't dead yet. When it is, Nintendo will probably tell us.