I've sent a snapshot to CTAN. Headlines:
- Correct an error if \tl_rescan:(N)nn is applied to an
entirely empty token list
- Introduce support for (u)pTeX
- New l3sys module to contain system/runtime-dependent
- New experimental \char_generate:nn function to create
tokens of (useful) catcodes in an expandable fashion
The main reason for the release was some issues caused buy the first
point: I will post separately about the other areas shortly.
Please give CTAN 48 h to install the update and for it to propagate.