So I think I'm probably the best placed to speak since I'm using fluidsynth both as a MIDI player and as a real-time synthesizer on Android.
Obviously I didn't wait for this feature to be implemented to create my applications, so I can say that I don't them... like at all.
for the player, I didn't tried 1GB SoundFont, but honest quality SoundFonts like Arachno and Fluid R3 works great and deliver a so much better sounds that the internal Android MIDI player, or other player I found on the Google Playe Store.
for the real-time synthesizer, again I didn't tried 1GB SoundFonts, but with a decent device (3-4GB RAM) I don't see why it shouldn't works...
And also, frankly, having a portable SoundFont MIDI synthesizer is awesome, but if you are really into that kind of stuff, the audio output quality of Android devices is not that great... and you need a real computer...with a real soundcard.
Anyway, I think dynamic sample loading is a great feature for device where memory is really an issue like embedded MCU etc...
just my two cents