There does not exist in French a true equivalent for the use of the preposition as a summing-up for a complement that has been used in the preceding phrase, complement that is apparently often an infinitival clause but not always. Instead, in French a pronoun is used : le, ça, y, en. (I have no certitude that there aren't more than four, though.)
- They are going to tell the mayor to do something about it. Are they really going to?
Ils vont demander au maire de faire quelque chose. Vont-ils vraiment le faire ?
- -- We'll have to go faster. -- Are you allowed to?
-- Nous allons devoir aller plus vite. -- Vous y êtes autorisé ?
- -- All the striking workers will gather in this place tomorrow. -- Do they have to?
-- Tous les travailleurs en grève se réuniront à cet endroit demain. -- Ça leur est nécessaire ?
- -- The teachers have the possibility to put pressure on the administration. -- Do they intend to?
-- Les enseignants ont la possibilité de faire pression sur l'administration. -- Ils en ont l'intention ?
The given example is translated as follows.
- Will you do the thing?
- I'm hoping to.
Ferez-vous cela/ça ? or le ferez-vous? (formal) _ Vous ferez ça/cela ? (colloquial)
Je l'espère.
Instead of "Je l'espère." the speaker may however say "J'espère ça.(!)" and adopt any one tone of voice in a variety of them from self-assured to cocky or angry, so as to connote his/her state of mind; of course, that can be associated with only a particularised context and not the most general one.