I can't remember too many times I thought that someone had a legit shot at breaking the streak. The one time I really thought it was going to end was at Wrestlemania 21 when he fought Randy Orton. I can't remember what struck me during that match but they were just started really pushing Orton then and it just seemed like that was the time.
I doubt the streak will ever end as well. But ending it would be the HUGEST rub a heel could ever get.
04/24 - Nile
05/18 - Abigail Williams
06/20 - Negura Bunget
07/04 - Agalloch
08/23 - Alice in Chains
12/06 - the Music of Final Fantasy