Brutus, thou sleep'st: awake, and see thyself / Shall Rome, etc. We often use the word "etcetera" to express boredom with ideas that seem only too familiar, but that's not the case here. Brutus is not substituting "etcetera" for something in the letter that he's heard before; the concerned citizen (actually Cassius) wrote "Shall Rome, etc." The idea is that, as Brutus needs to awake to the fact that he is a natural leader of Rome, he also needs to awake to the fact that Rome is in trouble. The "etcetera" serves to remind him that he already knows what is wrong.