I suspect that from the perspective of the French tax office, any form they send you is a convenience, you are still legally responsible for submitting all required information on your own. Since there is no general registration system in France, the best is to contact the tax office directly and give them your new address as soon as you have one:
Afin de recevoir votre déclaration à votre adresse à l'étranger, n'oubliez pas de l'en informer.
Source: Moving abroad on service-public.fr. There is also a link to a form you can use to report your income for the year in which you left France.
It might also be possible to report your income online or to get more info from the “Service des impôts des particuliers non-résidents”.
Finally, there is a useful service on service-public.fr that can be used to inform the tax office, big utilities, the social security/pension/welfare organizations and the department in charge of motor vehicles of you new address all at once but unfortunately, it's only available if you are moving within France.