As discussed in http://blog.vyos.net/vyos-1-dot-2-0-development-news-in-july , there's an idea to drop compatibility with Vyatta Core versions older than 6.5 that Kim and I discussed.

Right now, it is theoretically possible to load configs from Vyatta verions going back to XORP-based releases from 2007. If someone really wants to check if it works, I still have the images. ;)

The main concerns are:

1. Vyatta Core older than 6.5 is now six years old, and is nearly impossible to find in the wild, therefore no one tested those script for ages and no one is ever going to
2. Vyatta 6.5 itself is not perfectly compatible with older releases, for example the much missed "modify" firewalls always have to be manually converted to "policy route" rules, and automatic conversion is impossible because the latter only has partial functionality of the former
3. If someone still has one such router, they can always upgrade through VyOS 1.x, whose images we were never planning to delete after 1.2.0 release
4. Old scripts are a mess, using XorpConfigParser that is an even worse mess.
5. Removing them will make it easier to switch to a better system of storing current versions and running migration scripts