Learn Portuguese (Portugal): Onde estará o homenageado agora?

This is the epistemic use of the future tense. Instead of talking about the actual future, estará is used here to express speculation, probability, or wonder about the present moment. In English, we usually express this by saying 'Where could he be?' or 'I wonder where he is.'

How would the meaning change if I just asked 'Onde está o homenageado agora?'

Asking with está is a simple, direct question expecting a factual answer, like 'Where is the guest of honor?'. By using the future tense estará, you turn it into a speculative or rhetorical question, showing that you are guessing or wondering about his current location.

Could I use the conditional tense (estaria) here instead?

You could, but it would shift the timeline of your speculation. The conditional (estaria) is typically used to wonder about the past, translating closer to 'Where could he have been?'. Since the sentence explicitly includes agora (now), you need the future tense (estará) to speculate about the present.

What is the grammatical origin of the word homenageado?

It is the past participle of the verb homenagear (to honor or pay tribute to). Here it functions as a noun to mean 'the honored one' or 'the guest of honor'.