If they still manufacture rifles and brass etc. in the calibre it's not obsolete.
An interesting point of view and probably the single most accurate evidence that can be offered to support the life or death of a cartridge. Another is how many loadings is the chambering offered in. All the major ammo makers offer 2 if not 3 or 4 loadings for the 30-30. Several loadings are offered in 243 Winchester, but go looking for 257 Roberts. Yet the 257 in full pressure loadings is superior to either of these.
That is where basing the obsolesence of a cartridge on ballistics fails. Teh 284 Winchester is another example of a cartridge ofering superior ballistics yet is for practical purposes dead, the 6mm Remington is yet another example. There is a long list of cartridges that have been offered and failed the test of time.
Ballistics are not the only criteria that make or break a cartridge. The 284 Winchester doesn't do anything I can't do with a 270. If I owned a 270, I wouldn't trade it for a 284, whats the point? Same can be said of several of the latest "magnum" offerings. I figure we will see several of those fall by the wayside pretty quick.
The 30-30 continues to succeed because of two reasons. First, the rifles it is chambered in. By and large, say 30-30 and images of light easy handling easy carrying lever actions come to mind. Although the 30-30 has been chambered in every action type except an auto, it is the levergun we think about. The second reason is that it is quite mild mannered. Light in recoil, yet packing plenty of punch, it has a well earned reputation as a deer rifle that far exceeds its paper ballistics.
In fifty years of ballistically superior cartridges, the 30-30 keeps bringig home the venison while so many of the latest greatest offerings become mere flashes in the pan. No need to trouble with singing the praises of the 30-30 to the uninitiated. If you have to explain it, they won't understand anyway. The success of the 30-30 doesn't lie with curing those with magnumitis. The success of the 30-30 lies in it's being carried by those who have the choice of carrying something else.