Java 8 : How can it precede Java 7's general adoption

I'm finding more and more news about Java 8 - however, Java 7 is just now being adopted in a lot of places. For example, at my work, we are still on Java 6, even though some of us have Java 7.

Im wondering - what is the limit on Java available versions? How often can we expect a new Java spec to be rolled out and implemented. I always thought that Java 8 would be far in the future, since Java 7 was still evolving.

Maybe there is a good (non tl;dr) official source for these sort of details which I'm missing, if so, please let me know.

Solution

There were 2 options: 1. Wait with Java SE 7 until all feature are ready 2. Release Java SE 7 now (Summer 2011) and Java SE 8 soon afterwards with the remaining features

Oracle chose option 2.

Note:

Java SE 7 hasn't been released for end users yet, just for developers: https://www.java.com/en/download/faq/java7.xml
There is only a preview version out for Mac OS X: http://www.oracle.com/technetwork/java/javase/downloads/jdk-7u3-download-1501626.html
Java SE 6 goes EOL at November 2012 (given that the end user version of Java SE 7 is released at least 6 months before): https://blogs.oracle.com/java/entry/eoling_java_se_6_javafx