DLC

[LunaMoo]

The only time when emulator could simply "download dlc's" for game would be:
- when game doesn't require updates to use them,
- when those dlc's are hosted by game dev/publisher on separate site that doesn't require any accounts to download.
A situation like that practically doesn't happen and if it does like it's the case with user made "DLC's", just use a native web browser in your system.:]

PS Store connectivity which means messing with SEN accounts is a no-no, not only it would bring Sony's unwanted attention and loads of safety&legal issues, even the real PSP's aren't properly supported on PSS anymore, so it's not worth the trouble.
Also most dlc's need game updates and those require decrypting it on real hardware first since we don't have the keys to do that and since it's 128 bit AES quite possibly never will. Doubt any hacker even tried through since it's something that would only be useful for the very specific case of emulators(including official emulators on PS3 and PSV which also lack those).

Realistically a new user who doesn't store backups of stuff obtained when it was released and decrypted where required, will have a hard time getting any even free dlc's to work on emulators and no legal download that could be provided by emulator would really have any effect on making it easier.

So short answer - most likely never.