Although Android Kitkat (ver. 4.4) announced by Google, there are many devices pending to get Android 4.3 Jelly Bean firmware updates and the good news came from a French carrier SFR that they planned to roll out Android 4.3 update to Samsung Galaxy S4, S3 and Note 2 as well starting from this October. However, there will be no 4.2.3 update for S3 and Note 2 smartphones but these devices will be direct upgrading to 4.3.

In August, Google has already rolled the Android 4.3 update for HTC One and Galaxy S4 Google Play Edition phones and the rest of the S4 models to get the update in October month across the globe in scheduled time. SFR of France is the first carrier announced the roll out, many other carriers worldwide will follow.
If you are upgrading your device from version 4.2.1 to 4.2.3, then the excitement of the new update will be limited to the incremental upgrade to the previous OS with new security features such as SELinux and restricted profiles. Here, Galaxy S3 seems to be the lucky device, which is a 1-year-old device to get the latest version of Android.
The French carrier SFR just announced the details and schedules of its devices and receiving updates. According to the time table, Galaxy S4 to get the update on this October and S3/Note 2 to get in late November, soon after the completion of S4 roll out. The updates can be installed via Samsung KIES or via OTA. Along with Samsung smartphones, HTC One to get the 4.3 update in October but only option would be via OTA only.