Condicional vs perfect future

Hola Felix

Yes, you can use the perfect future instead of the conditional. For example, in this sentence from the lesson:

-Arturo tuvo un final triste. -Tendría un final triste pero vivió una vida de lujo.

-Arturo had a sad end. -He may have had a sad end but he lived a luxurious life.

You can express the same using "-Habrá tenido un final triste pero..."

However, if the first statement is using the pluperfect, although you may use the perfect future too here when stating an objection or disbelief, it wouldn't sound very natural. The natural tense to use in this case is the perfect conditional:

-Javier había prometido invitar a todos si aprobaba. -Lo habría prometido/ lo habrá prometido (less used, less natural)  pero no ha habido ninguna invitación.

-Javier had promised to invite everyone if he passed. -He may well have promised but there has been no invitation.

Saludos

Inma