Complex sentence: In 2013, it was announced that MODX 3 would be released by the end of the year, but this has been pushed back to an indefinite date, with MODX 2.3 acting as a major interim step.
Split into simpler sentences: In 2013, it was announced that MODX 3 would be released by the end of the year. This has now been pushed back to an indefinite date, with MODX 2.3 acting as a major interim step.