Although, it's very possible that it'll be 3GB partitioned for apps, which is what the Photon has. Here's the breakdown of how the 16gb was partitioned on the Photon:
8.92GB - internal storage (whatever you'd like on here)
3 GB - apps only
4.08 GB - Split up between Room for future updates and other miscellaneous needs for the phone
What I didn't mind about this partition was that, I already had an external 32GB SD card and when moving the apps to SD, it would go into the internal storage partition (not the external SD). Some didn't like this, while I found it was easier to manage the files that were needed and the ones that weren't.
That said, there's no guarantee that HTC follows the same partitioning, but figured I'd throw that out there since the 3vo only had 4GB.