I don't think it is in the cards.. it has been requested several times but I don't recall hearing or reading from the developers that they planned to incorporate it in the near future.
Note that you can enter multiple keywords in the Ctrl-K dialog at once by separating them with semicolons (just ';', no spaces). It's also possible to autogenerate keywords from folder names (eg. "d:\vertebrates\mammals\cats\lion.jpg") and images can be assigned to (multiple) galleries. Depending on the nature of your images, keywords and cataloging needs, it may be possible to work out an alternative strategy using these and other features.