Learn Italian: In futuro sarò molto felice. - In the future, I will be very happy.

sarò is the 'I will be' form of essere in the future tense. essere is irregular here: instead of building on its infinitive, it uses the special stem sar-. To make the 'I' form, we add the standard future ending -ò to get sarò.

Why do we say In futuro instead of Nel futuro to mean 'in the future'?

When talking about the future in a general sense, Italian uses the simple preposition in without an article. You would only use nel futuro if you were talking about the future of a very specific thing, but in futuro is the standard set phrase for 'in the future'.

If a woman is saying this sentence, does she need to change felice to match her gender?

No, felice stays exactly the same! Adjectives that end in -e in their singular form are used for both masculine and feminine subjects. It would only change to felici if there were multiple people (plural).

Could molto change to match the speaker's gender, like molta felice?

Not in this sentence. Here, molto is acting as an adverb meaning 'very' to describe how happy you are, and adverbs never change their endings. molto only changes to molta, molti, or molte when it describes a noun, like in molta pasta (a lot of pasta).