I wouldn't exactly hold my breath on the maps for Black Arrow. Seeing how BA is a Xbox exclusive - there isn't an actual PC equivalent to use as a level designer as there was wth the Raven Shield release. Using the unrealED with textures and meshes from the original release of Raven Shield made it much easier to develop and troubleshoot the map compatibilities - and for those not familiar with converting maps there are a number of things either in the map or the config files that have the potential to make the maps incompatible.
If in fact the maps did get ported, I wouldn't at all be surprised to see them not usable in total conquest or retrieval mode. The simple reason for this is without a PC editor to add in things like where the containers spawn, or where the drop off sites and satellites are located the task of making maps compatible becomes even more difficult. I wouldn't say that it can't be done - but it sure will take a lot of talent and patience to make them run properly. I don't expect this will be a quick thing, if it's something that we see ever....
However, I sure do hope someone can prove me wrong... I'd love some more maps for Black Arrow.