While I would never begin to speak for Tom, but the way I read this is not data won't live on appropriate speed media. If that's your idea of tiering, then cool.
What he's saying is a dying idea is the idea of having software manually move datasets between tiers. I don't want to have to move my database from SSD to FC/SAS, to SATA and vice versa.
Rather, imagine a world where everything really lives on SATA or some equivalent cheap/deep/slower storage and Flash (whether PAM, SSD, whatever) is used as a read (and potentially write) cache to speed up the exact workload that is being used.
This is kind of like the HSM (hierarchical storage management) idea. It was a huge buzz word in its day and largely didn't work because people wanted HS, but no one wanted the M part. Caching algorithms kind of do that automatically, so why implement yet another software layer to try and figure out when to move datasets and then go through the pain of moving them when caches basically do the same thing for free (since just about every storage system does some of caching today).
So I suppose it depends on what you mean by storage tiering. I see what Tom is talking about is the idea of moving whole datasets between tiers using specialized software to do it. Caching can do the same thing, but much simpler.
Just my take. This is an interesting discussion...looking forward to seeing what folks think.
