Pretty sure they will but the question is when. Best evidence for that is their new manuals. On the Marlin website at the bottom of the specs page for the 1895 they have a link to the new manual. In that manual at the top of page 19 is the sentence:
'Ammunition Notes and Warnings:
NOTE: If your rifle is chambered for 444 Marlin, .45-70 Gov’t. or 450 Marlin,
please carefully review the following warning and dimensions."
Under the two models they haven't introduced yet, the 336 and 1894, the instruction manual link has an asterisk warning: "* Ruger was not involved in the creation of these manuals and cannot verify the accuracy of the information provided in them. We offer these manuals only as a courtesy to pre-Ruger Marlin firearms owners."
So by deduction if the new Ruger-Marlin manual lists the .444 and .450, that's a pretty good bet they'll eventually offer those.
