DECNet is one. As far as I can tell, most all other efforts so far have been privately conducted and have been resulting in patents, which is not appropriate for the internet.
VTP is another. This one more popular, but only serving the wireless niche. I don't know what kind of added security features it offers in relation to TCP/IP, if any.
IPv6 is supposed to increase security by integrating the IPSec protocol into the new IP protocol. This has the potential to disseminate the use of IPSec, me thinks. Currently it supports IPv4, but is optional. Which means it's rarely used. But if IPv6 gets some speed from this slow start, it's quite possible it IPSec becomes widespread.
Note that both DECNet and VTP offer TCP/IP translation services in some way. So there is really no danger of coming with something new. Just a lot of work and presumably a very long period of adoption.
