It's not that simple at all. For one thing, having a v6 network doesn't mean you can't have a v4 network. You can run v4 in exactly the same way you currently do, with exactly the same software, and it'll work no worse than it already does.

But for another, the v4 space is available as a subset of the v6 space:

  $ ping 64:ff9b::8.8.8.8
  PING 64:ff9b::8.8.8.8(64:ff9b::808:808) 56 data bytes
  64 bytes from 64:ff9b::808:808: icmp_seq=1 ttl=113 time=9.82 ms

That's from a machine on a network with no v4, and it works fine. I can reach v4-only sites from it too. I could even do this using v4 addresses if I wanted, but if I showed you the output from that you'd just claim I was using v4.