there will be additional latency and significantly more overhead involved in routing IPV6 traffic
Errmm.. I think you would actually find out that with some IPv6 features like route aggregation and the checksum-less IPv6 header, things should be faster. But yes IPv6 routing without hardware capable of switching IPv6 packets will definately be slower.
If the entire net were converted to IPV6 today, it would melt.
The only reason it's going to melt is because the majority of "IPv6 support" out there uses software-based routing
Fortunately people will likely continue to use IPV4 for a long time and the IPV6 traffic will grow slowly enough that router technology will improve as necessary.
Router technology IS already here. Most hardware vendors already support IPv6 switching.