We're launching the release of iText 5.4.3 and as promised, we've been working on PAdES-5 and PDF/A. We already supported signing XFA forms using XML-DSig, now we also have support for signing using XAdES (which is required to meet the PAdES-5 standard). For the moment, only BES is supported (EPES will follow).
In the next couple of releases, we'll continue working on PDF/A, more specifically on PDF/A-2 and PDF/A-3. Again, this doesn't mean, we don't support PDF/A-3 yet, as a matter of fact, iText is ready for the German ZUGFeRD standard.