Eclipse Juno (3.8/4.2) is scheduled to be released today (June 27th). However, the current stable build of Liferay IDE (1.5.3) is not compatible with Eclipse Juno. It will be a few more days before I can create a new stable build of Liferay IDE (1.6.0) since there are a few remaining issues that need to be resolved.
However, in the meantime we are going to make a Juno compatible build of Liferay IDE available on the nightly build updatesite. Here is the new one that you can use for Juno (updatesite should be available by the 27th).
Please report any issues or regressions that you find in Liferay IDE features for Eclipse Juno either in JIRA under IDE project or in the Liferay IDE forums.