Not if I can spoof my IP6 address as easily as I can spoof an IP4 one, nope.
One thing about IPv6 is that you cannot scan the entire address range looking for open (memcached or other) servers like you can with IPv4.
Turns out that is not as true as you would think in practice.. you can reduce the search space significantly because of known IPv6 prefixes, EUI-64, a MAC address database and trying a few additional likely addresses such as ::1 ::fffe etc
But servers will almost certainly have a DNS entry. So they aren't really hidden in the immensity of the address space.
Would they be publicly resolvable? And even if they are, how would you find the name? Wouldn't a lot of these machines be internal infrastructure of various companies?