According to a document posted up by Android Police, which has since been removed, Android's next major operating system, known as Key Lime Pie, will be launching this spring. The document, which apparently belonged to Qualcomm, had details that suggested just this. The removal request could indicate the details were accurate.
Google's I/O conference is scheduled for May 15-17, which would be a great place for the next version of Android to debut. Who knows, maybe they'll hand out upgraded Nexus 7's running Key Lime Pie. We'll be sure to keep looking around for details regarding the next version of Android, including features that will be included or possible release dates.