I'm probably this forum's biggest Clara fan. I love her. But even I can't see how Moffat would bring her back without REALLY cheapening her death and also not staying true to the character arc she went through in series 9.There's a few early reviews out now (surprised the Beeb didn't want to keep this one secret) and there's a couple of common threads running through them; that it's not the episode the trailers are leading us to expect, that there's a controversial appearance halfway through (Zombie Tennant?) and hints that Clara will end up getting the patented Moffat Get Out Of Death Free card after all.
All Clara wants to do is travel with the Doctor. If they bring her back (that is, Clara proper, not Oswin or a splinter), especially since Jenna is leaving the show this very episode, what are they going to do? Short of having her steal her own TARDIS and have her own adventures (which is the ending I'd always hoped for her, personally), how do they justify that?
She won't go "Okay, so I died living this life and I was given a second chance by the Timelords or whatever, so now I'll be a good girl and play it safe and teach at Coal Hill." She'd want to travel more. The Doctor will be thrilled to have her back, only to say "Traveling with me got you killed. Time to go home."? That would be as lame as their lying "hug" in Death in Heaven.
Whoever they "regenerate" in the episode, I don't think it's Clara. If it is, they better have a good reason for it.