A few verbs, among them in particular verbs of perception like sehen, can use a special construction called accusative and infinitive. In that construction, the plain infinitive without zu is used, and the person being seen doing something is put in accusative.
So your sentence isn’t far off, there is only a small word order issue: The second part of the main verb (if any) goes at the end of the sentence, after the accusative and infinitive:
Hoffentlich werde ich euch (acc.) eine neue Fremdsprache lernen (inf.) sehen.
Hoffentlich sehe ich euch (acc.) eine neue Fremdsprache lernen (inf.).
Commas can’t be used here.
Instead of an accusative and infinitive construction, a subordinate clause can always be used:
Hoffentlich werde ich sehen, wie ihr eine neue Fremdsprache lernt.