In some ways I think we have been living with unnecessarily complicated input forms with MARC as it is. I hope linked data means that we can have something more akin to a web form where the underlying mark-up is not laid bare unless necessary. I upload all my photos to Flickr and add, titles, descriptions, and tags and assign them to groups and albums: I have no idea how this is actually recorded and nor do I need or want to. I imagine it not being quite as extreme as that as librarians will also need to manage the data and think about how it is actually shared or displayed, and so on, but there is certainly no need I think for cataloguers to be hand-crafting triples in xml or turtle.
Have you seen the Bibframe editor? http://bibframe.org/tools/editor/ This gives one example at least of what an editor might look like. There is also a Zepheira version here: http://editor.bibframe.zepheira.com/static/
I think it’s also worth suggesting that an increasing amount of our records (a majority by volume if not by time spent) are not individually edited, being downloads from various suppliers which are edited and managed in bulk. In many ways, what the future version of a Marcedit (Linkeddataedit/Bibframedit?) equivalent looks like, or how usable linked data APIs are, is as important as an editor for individual records.
Head of Current Cataloguing
Senate House Hub
University College London
London WC1E 6BT