3
If you upgrade to 2.2.4, you will wait a slightly longer period for an upgrade to 2.4.
I would recommend to you to continue using your current version until 2.4 has come out. A script for the upgrade will be made available at that time. There is a script for the 2.0.x to 2.2.x series, but you may encounter some bugs depending on your server environment and many other as of yet, fully unnaccounted variables.
I strongly reccomend that you use the 2.0.13 series on your production sites for the time being, as this is the most stable version.
Upgrades are available to upgrade your 2.0.9 version to 2.0.13.x in the downloads secion of the site. This is as far as you should upgrade for the time being.
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