General:
* Prochainement: This is the most general and straightforward way to say "soon to be." It literally means "next" or "coming up."
* Bientôt: This means "soon" and is also commonly used to express something happening in the near future.
* Dans peu de temps: This literally means "in a little bit of time," and is more specific than "bientôt."
More specific:
* À venir: This means "to come" and suggests something that will happen in the future.
* En passe de devenir: This translates to "in the process of becoming," and implies a transformation or change into something else.
Example sentences:
* Elle sera prochainement maman. (She will soon be a mother.)
* Le livre sera bientôt disponible. (The book will be available soon.)
* Dans peu de temps, il sera diplômé. (He will be graduating soon.)
* Un nouveau restaurant est à venir. (A new restaurant is coming soon.)
* Il est en passe de devenir un grand acteur. (He is on his way to becoming a great actor.)
The best choice will depend on the specific situation and the nuance you want to convey.