GameSpot has some details from an Interview of SCE Software Platform Chief Izumi Kawanishi that was published in Japanese magazine Famitsu.

Besides making the Sony PSP browser more usable and improve direct video downloads and also maybe introduce streaming video, the most interesting discussed future feature is an email client for the PSP. Sony actually thinks beyond text emails. The company considers to introduce video and audio communication.
For video communication obviously a video camera is necessary. This would imply Sony is planning to come up with a Video camera accessory for the Sony PSP. To do text emails on the Sony PSP a keyboard is also necessary. The PSP keyboard that surfaced a while ago, is supposed to ship end of October.
More details on GameSpot (Thanks Larry R.). With the help of I4U readers we published a future feature wish list for the Sony PSP a while ago.