The Galaxy Fold 4 has been announced, price has dropped for the 512GB model compared to the Fold 3 and there's now a 1TB model. It's more of an incremental upgrade compared to the jump from the Fold 2 to the Fold 3.
Changes:
A tiny bit wider - 23.1:9 vs the Fold 3's 24:9 on the front, 6:5 vs 5:4 on the inside display
New subpixel matrix scheme that's meant to look sharper
More hidden under-display camera
Android 12L
Larger camera sensor vs the Fold 3
Higher-res main sensor (50MP) vs the Fold 3's 12MP
3x optical zoom vs 2x
Snapdragon 8+ Gen 1
Slightly lower weight (263 vs 271g)
45% stronger ultra-thin glass screen
Stronger adhesive on preinstalled screen protector
Nice summary of the changes, pretty underwhelming event overall although I don't think anyone was expecting much.