In answer to a question from AGenheimer , I have pasted in the "Duolingo "Tips and Notes" for the future tense. This info may be helpful.
Now, to answer your question, "still, why not 'spriche'?" The infinitive form of this word is sprechen. So that is what goes at the end of the sentence.
Also, spriche is right in the present tense. I'll paste the present tense conjugation of sprechen below.
AGenheimer, no the verbs at the end of the sentence are not conjugated in the plural--they are in the infinitive. Often, the infinitive will be the same as what you are calling "the plural". I am pasting below the "Tips and Notes" from the first Duolingo unit on the future tense. But just to sum up, if you're using werden for the future tense, the only verb in the sentence that gets conjugated, is werden. Any other verbs should be in the infinitive, and they go at the end of the sentence.
Tips and notes
The future tense consists of a conjugated form of werden in the present tense and an infinitive (the base form of the verb).
ich werde spielen------I will play
du wirst spielen---------you will play
er/sie/es wird spielen---he/she/it will play
wir werden spielen------we will play
ihr werdet spielen-------you will play
sie werden spielen------they will play
Sie werden spielen-------you will play
Depending on the context, "ich werde spielen" translates to "I will play" or "I am going to play". In German, there is no distinction between "will" and "going to".
German normally uses the present tense to indicate the future. For example, "ich gehe morgen ins Kino" translates to "I will go to the movies tomorrow".