Until Content Translation is able to provide suggestions, we can redirect users to an existing tool that helps finding articles to translate. The transition won't be as fluent as desired, but it may be useful still.
This can be integrated into the dashboard or the "new translation" dialog using a link like "Looking for ideas on what to translate?".
If we have information on the source or target languages (based on user current or previous selections) we can pre-fill the language parameters on the URL so that the user does not have to select the languages again. An example of URL for Spanish-to-Catalan is http://tools.wmflabs.org/not-in-the-other-language/?lang1=es&proj1=wiki&lang2=ca