Based on the descriptions provided, it sounds like Ocean A has a prominent feature that resembles "baseball stitches," which may suggest tectonic activity or potential rifting. If Ocean A is subject to geological processes that could lead to its division or shrinkage, it might get smaller over time. Conversely, Ocean B, with volcanic activity, indicates that there might be new land formation or changes happening due to volcanic activity.
Given this context, the most likely prediction would be:
Ocean A will shrink, and Ocean B will get bigger.
This is because the tectonic activity in Ocean A might cause it to diminish while the volcanic activity in Ocean B could lead to its expansion as new land is formed by the eruptions.