From my personal experience, and I don't mind to be judgmental here, I think the biggest challenge facing ROCOR is going to be expanding its church beyond the Russian ethnic group. Despite making more inroads than other Orthodox churches with non-ethnic converts, ROCOR is still overwhelmingly a Russian Church. I visited three ROCOR churches in Canada and all three had 99% Russian congregants, with the entire liturgy and sermon in Old Slavonic/Russian.
Well, I know a lot of people will hate to hear this, but is it really a bad thing for Americans to adopt Russian customs? Which culture really has been more successful at engaging in large scale spiritual warfare over the past century of history?