Ok I'll bite...
(or should that be Byte in this context ;)
To be fair new technology always takes a while to displace the incumbent technology. For example no moving parts Flash is better than spinning disks, yet we still have cheap disks which get ever better. Its going to take some time before Flash reaches the densities needed to displace spinning disk drives in all market areas.
The same is true of even newer technology, like PCM, where its first sold to high value niche markets, before they can then start to sell it to higher volume mass markets, where its price will finally fall.
That's not to say PCM is going to finally win, there are as you say other competitors fighting for the same place in the market. PCM is much faster than Flash so it will win in any market that needs speed. PCM also suffers less from Memory Wear (PCM survives for about ten thousand times more writes than Flash so there will definitely be markets for PCM over Flash).
I think the biggest differentiators from Flash will be memory Density and Memory Wear (as they are the mass markets), but which memory technology will win in each of these areas, who knows yet. But bigger densities will win market share in all existing storage applications. But the even bigger one (and the biggest unknown) is going to be Memory Wear. If someone comes up with a technology that doesn't suffer from Memory Wear but also has the large storage capacity of Flash combined with the speed of DRAM, then they win massively if that is comparably priced.
The biggest problem I think PCM has is simply the potential Memristors have. That will (currently) scare off investors in PCM and other technology until weaknesses in Memristors are more clearly confirmed as weaknesses (which market areas will it be slow to move into highlighting its weaknesses). Currently its hailed (often by its creators) as the holy grail of circuit design and in many ways it is *in theory* ... The problem is we have yet to see mass market Memristor drives. Memory Wear however is likely to be Memristor's Achilles Heel. Its not going to be a DRAM replacement until the Memory Wear problem is totally solved and as far as I know it hasn't been (it would be huge news if it has been solved!).
So anyway PCM isn't a direct competitor to Flash, they have different markets, its just the elephant in the room is Memristors which would worry any investors in other memory technologies like PCM, at least currently.