I think it's great that he's comfortable with Ethereum Classic project and has no interest in hindering the project. Now if the ETH community can get behind their leader and support that decision it would be great. Be nice to get a little more harmony in that space.
This will be good for everyone. The original Etherem classic supporters should appeal to the miners and mining pools supporting the fork to point their hashing power to the original. Since it is ok for Vitalik to have both chains running side by side then I guess it is ok for their community to crossover and participate in the original and honest chain.
Your suggestion that miners abandon one network to support another based on what Vitalik said won't interest miners in general. That said if merged mining was introduced the vast majority of miners would support that and mine both coins (more profits). This would give both coins ETH and the original ETC a more secure network.
I doubt the Ethereum network is currently capable of merged mining since that has to be done by design. It's been done multiple times with other coins for example the Litecoin network currently supports the Dogecoin network (without this support dogecoin would have very poor security).
Definitely if merged mining is added it will help re-introduce the concept of community into Ethereum space.