While it should be possible to swap out the memory card on the new iTunes phone for one with more capacity, the person who has seen the handset says the phone's software appears to artificially cap song storage at 25 songs, regardless of how much memory the phone has.
Still, having to hot swap between (expensive, proprietary) memory cards on the Vita kinda flies in the face of large storage capacity memory cards, like the 32GB one employed by the unlucky person who discovered the limitation.