Does 'Other creatures you control have intimidate' affect new creatures brought out?
It will affect all your creatures for as long as you control it; whether those creatures were there when you first cast it or not. Your creatures will lose the bonus as soon as you stop controlling it. This is called a static ability, which generates a continuous effect. It's described in detail in this rule:


  604.2. Static abilities create continuous effects, some of which are prevention effects or replacement effects. These effects are active as long as the permanent with the ability remains on the battlefield and has the ability, or as long as the object with the ability remains in the appropriate zone, as described in rule 112.6.