Is there a future for painting when we have photography? Obviously there is, just in a different capacity - we're no longer painting to record reality as it looks (because we have photos and video for that), but to produce images that photos cannot.
Pixel art done for strictly practical, non-aesthetic purposes has been steadily becoming rarer over many years, and pixel artists have instead moved on to exploring its aesthetic strengths. Not many people are bothering to pixel-polish icons and emotes anymore, and that'll be even rarer as higher resolutions become common. Is that really a loss worth worrying about? I say it's not.
The ease of creating high-res art hasn't killed pixel art, but has instead allowed pixel artists to focus on pixel art's strengths and incorporate those into their work. Pixel art has largely become an aesthetic rather than practical choice, and the "pixel" in pixel art rarely corresponds to actual physical pixels these days. We already view most pixel art games zoomed in rather than at 1x. As screens get larger, we'll just be zooming in more.
Something else to consider with larger resolutions is that even though the physical pixels get smaller, they largely retain their clarity. The clean, crisp colours and shapes of pixel art intended to be seen at 1x will remain clean and crisp even at 4k and 8k. And as I mentioned, art intended to be seen zoomed in and up close will just get zoomed more. With higher-res screens, zoomed in pixel art will probably actually look better because artefacts from uneven zooms will be less noticeable.