Why a future battlecruiser might be called a cruiser

Are battlecruisers or gun cruisers more likely to return?

Probably gun cruisers, especially if railguns mature, although the eventual name may change for political reasons.

Railgun-armed ships would probably be described as cruisers rather than battlecruisers. Even the cruiser label may acquire a substitute because of its political and imperial associations. This is explicitly a forecast, since neither the technology nor its future classification is settled. A familiar operational role could still reappear under different institutional language.