RPKI is great, and I use it for everything except for two /24's that I got pre-ARIN. However, RPKI won't help with the situation where some kind of compromised host is worming its way through the internet running nmap against everything. Most of the IP addresses showing up in our dragnet are in fact announced by the very ISPs that own them. Most of these do not appear to be bogons.
I don't think RPKI will do anything to stop threats or DDOS attacks that happen currently. It should stop rogue route updates though.
It will, however, stop projects like these from blacholing IP ranges belonging to others
It's not blackholing anything for anyone other than the subscriber, so this doesn't cause a block for anyone who isn't participating