IMO, the Sabattis will have ZERO effect on the vintage double rifle market.
As Curl says, not the same breed of cat.
In fact, I can not think of a single example of new firearm which has caused the established vintage market to drop at all. If anything, the opposite is probable by simply raising awareness where there wasn't any before.
Take Winchester 1895's for example.
Once the new 405's became available and ammo was once again common, the vintage values shot way up.

BTW, it looks like Cabela's has the lower priced model in 45/70 too.
http://www.gunsinternational.com/A-Cabel...un_id=100108784