The biggest area that this new pi might effect is any future enhancements to the wallet or coin. I would expect that the older pis would be to limited in power to do much in the way of adding new things to the wallet.
I would also think that the new pi my reduce the time it takes to verify a blockchain download. My B+ took the better part of 1 week to do a fresh download and verify of the block chain after I did a fresh raspbian install.
I'd love someone to correct me if I'm wrong, but I think reading the blockchain is more HDD/RAM-based than CPU. At least from my experience, when the system is syncing, my HDD read speed and RAM usage shoot through the roof, while the CPU isn't affected much. And when syncing is done, HDD/RAM both cool down.
It dose indeed depend a lot on Hard drive speed and indeed, i use a 16 GB class 10 card for the blockchain, not an external drive, so that can affect my personal results but I also know that if you have the extra RAM ( as the new pi dose ) with the extra CPU cores, you should see an improvement in speed. it is hard to say because a lot goes into performance on a system. The hard drive and RAM do not work independently of everything else on a system, so, depending on the application and type of data you can see no change or a really big change in speed.
I would also think that you would want efficient systems that can scale with the higher number of transactions the network might see if the coin really takes off. In any event, since I will be getting a V2 Pi for other applications anyway, there is no harm in seeing if the thing has any speed advantages.