"J'espère qu'il portera celui que je lui ai acheté."

Translation: I hope he will wear the one I bought him.

[waakak]

"I hope that he wears the one that I bought him" should be accepted even though the french word is technically in the future tense. "wears" in English in my sentence can easily refer to the future.

"What shirt is he going to wear tomorrow?"
- "I don't know but I hope he wears the one I bought"

It's the same kind of thing going on with sentences with "when". In french, two verbs separated by "when" referring to an event in the future must be in future tense. In this case in english, one verb is in the future and the other is conjugated in the present.

[JoyRingros]

'I hope that he will wear the one THAT I bought him' should also be correct.

[W-Ruggles-Wolfe]

Shouldn't it be "I bought for him"? («lui» is an indirect object)

[GrahamNdP]

The "for" is optional in English! :)

[RosaLomazz]

"I hope he will be wearing' was marked as a mistake.

[ILOKA2004]

Why isn't it. J'espère qu'il portera celui que je l'ai acheté

[ColinCanuck]

it's "lui", not "le" because you didn't actually buy him, you bought for him. Him is an indirect object.

[GrahamNdP]

You do not elide « lui » : « l'ai = le / la + ai » ! :)