It's imminent and now Virgin Media has added to their (increasingly informative) community boards with one dedicated to posts from those testing the update 15.2.
You can find it at http://community.virginmedia.com/t5/TiVo-Update-Pilot-Forum/bd-p/tivo_update but please don't flood it with questions to those with the the new software as that's not what it's for. An interesting read though: looks like boxes are faster, PQ may have improved (no real consensus on that, but then not everyone had a problem to start with) but no-one has yet mentioned any changes with PIN code requirement. I'll keep an eye on it and report anything I see of interest.
Universal padding is working but not everyone's happy with the way it has been implemented, but I've noticed that there are only a few people posting there at the moment so it may not be a representative view.