I don't think translating our work into French constitutes plagiarism if we're applying for funding, for example. If I publish an article in French, I definitely wouldn't have it translated for publication in English.
However, it would be interesting to set quotas for French-language articles published in bilingual journals. For a long time now, I've contributed to the Canadian Journal of Political Science, which is my favourite professional journal. I've even written an article on publication in French for that journal. Only one article is published in every one of its issues; all other articles are in English.
So how can we encourage the publication of articles in French in so‑called bilingual journals to which virtually no French-language articles are submitted? Many journals don't have translation departments either.