Shift from one scene to another (based on time)

Create a new scene, create an empty GAMEOBJECT, attach the following script to it

 var MaskTexture : Texture2D;
 static var depth : int;
 var fadeTime = 5.0;
 private var alpha = 0.0;
 enum Fade {In, Out}
 function OnGUI()
 {
     GUI.color = Color(1,1,1,alpha);
     GUI.DrawTexture(Rect((Screen.width / 2 - 685), -15.0, 1370.0, 768.0), 
     MaskTexture, ScaleMode.StretchToFill, true, 0);
     GUI.depth = 1;
 }
 // Fade in the GUITexture, wait a couple of seconds, then fade it out
 
 function Start () {
    yield FadeOnGUIAlpha(fadeTime, Fade.In);
    yield WaitForSeconds(2.0);
    yield FadeOnGUIAlpha(fadeTime, Fade.Out);
    Application.LoadLevel (Application.loadedLevel+1);
    }
 
 function FadeOnGUIAlpha (timer : float, fadeType : Fade) {
    var start = fadeType == Fade.In? 0.0 : 1.0;
    var end = fadeType == Fade.In? 1.0 : 0.0;
    var i = 0.0;
    var step = 1.0/timer;
    while (i < 1.0) {
       i += step * Time.deltaTime;
       alpha = Mathf.Lerp(start, end, i)*.5;
       yield;
    }
  alpha = end;
 }