It's too early to discuss this in detail, but I just wanted to shed a little light into our plans regarding this feature.
Tropy will be able to distinguish between a number of different value types. At the moment all metadata fields are essentially strings (using a simple text input field). Going forward, we are planning to add more types (e.g., numbers, dates, names) — each type will allow us to optimize search and sort capabilities (e.g., search for matches in family names only, not in given names) and utilize dedicated input widgets.
Furthermore, metadata templates will potentially allow to define a set of possible values for a given property.
All this is to say, that, yes, we will definitely be looking to add auto-suggest functionality, but at this point we have not decided on some of the details (i.e., will the feature be limited to certain value types, properties, or based on template information). Stay tuned!
As a final note, I would like to draw attention to the bulk-editing feature. You can currently select multiple items by cmd/ctrl clicking on several items (using shift is not yet enabled in the current beta) and edit the data of multiple items at the same time. If you have a number of items to which you want to add a creator, for instance, of an already existing item you can select the existing item first and then, using ctrl/cmd, select the other items: if you then click on the creator field in the metadata panel (which would show the creator of the first item you selected) and just press return all the selected items will be assigned that creator. (If something went wrong you can undo the change) Obviously, this is not the same as auto-suggest, but I thought I'd mention it, because batch editing may not be immediately obvious in the current beta due to the lack of selecting items with shift.