First Ruger made Marlin limited availability, You will be able to get "other" 45-70's but it won't the First Ruger made limited availability version. Just like they'll do with every caliber going forward, limited release/features until they can ramp up production numbers across the line up to offer slightly lower entry points.
It's pretty obvious on the webpage, right at the top besides the pic says
https://www.marlinfirearms.com/s/model_1895sbl/
INTRODUCING THE FIRST RUGER-MADE MARLIN® FIREARM
THE MARLIN® MODEL 1895 SBL
Now Shipping with Limited Availability. Please Contact Your Local Retailer for More Information.
Note: Ruger encourages retailers to contact their distributors for availability and advises consumers not to leave deposits with retailers that do not have confirmed shipments.
That has been their marketing strategy for years now, on most of their line-up.