Future wars will still demand Flower-class equivalents

Will navies need Flower-class equivalents again in a future major war?

Yes. Any large conflict will create more escort tasks than a few expensive warships can cover, and many future little ships may be uncrewed.

The requirement does not depend on whether a future conflict is fought only on Earth or includes more speculative theaters. Shipping and naval forces will still need escort across many routes and operating areas. The useful successor to a Flower-class corvette would therefore be inexpensive enough to build in large numbers rather than optimized as an exquisite one-off combatant. Many such small escorts may be unmanned, although their detailed form remains open. The technology may change, but the force-structure need for numerous escort platforms remains.