I also would like a 1st gen Colt SAA rechambered to a modern calibre that does not require registration. But "end runs," as someone called them, around the legislation certainly could result in future modifications to the legislation governing registration of antique firearms. The most common method appears to involve rechambering antiques from obsolete calibres to modern calibres. I suspect that it may only be a matter of time until government closes that loophole.
It appears self-evident that government intended the 1998 antique legislation and regulations to exempt true antiques, those guns chambered in obsolete calibres, from registration. The rules that we have played since 1998 designated as "antiques" those guns that were 100 years or more old as of 1998. At the same time, government added the calibre guidelines, requiring registration of guns made before 1898 in calibres that remained readily available as of 1998. At least that appears to have been the logic used by government in 1998. Obviously, government only intended to ease restrictions on guns in obsolete calibres.
Back in 1998, government officials must have realized that people could reload in the various obsolete calibres. But the lack of commercially available ammo in the obsolete calibres provided justification for not requiring registration of guns chambered for those calibres. Still today, one cannot readily buy ammo in .455 Webley, .44 Russian, and various other obsolete calibres. To allow unrestricted ownership of guns in those obsolete calibres still makes as much sense today as in 1998.
If, as someone suggested, the new legislation will require periodic reviews of the regulations, those regulations may well change in the future. If government's intention truly was and still is to register guns that can fire ammunition chambered in modern calibres, what do you think may happen in the future? It would be great if we could keep on using .45 ACP, .44 Special, and .38 Special in unregistered guns. But I would not count on it.