Leviathyn reports that patent documentation for a new version of PS Vita has been "found" (no details as to how it was found). And while there is nothing to verify the authenticity, the addition of HDMI and 4G support is small enough changes to sound plausible at this point. Sony released quite a few iterations of PSP during its run, so a new PS Vita model later this year is fairly probable.
With 4G support we may be able to play online without wi-fi... Here's hoping!