Joss was going to bring Tara back in the seventh season. He planned an entire episode about Buffy being granted one wish, no restrictions, and she would be debating the whole episode on what that wish would be but couldn't choose....and finally, at the end of the episode, she would visit Willow and talk about something shallow and superficial that she would have wanted (ex. shoes) Willow would be confused and ask if she used her wish for that, and Buffy would go, "of course not" and silently leave the room. And then Willow would turn around....and Tara would be standing in front of her.
But unfortunately, even with Joss fighting and fighting for this concept to happen, it just didn't work out for whatever reason, and they had to let that idea go.
WHY DID IT NOT GO THROUGH? OH MY GOD THAT WOULD HAVE BEEN PERFECT. AND JUST, OMG TARA!
I've been Buffy watching for the last few days, like just marathoning episode after episode, so I'm just on a Joss Whedon kick at the moment. Soon will be moving onto Angel.