I suspect that Artains will be like World's Kulve Taroth weapons and eventually get a MR upgrade
Its a popular take in the online MH community to want artains to be phased out or straight up removed in the transition to master rank but I personally suspect that we're gonna get MR variants like in World: Iceborne's Kulve weapons (despite it being an unpopular choice)
They already gave artains an upgrade under the reasoning of "not wanting to waste the time people used for artains" and I think they might do the same justification for giving MR variants. This is on top of the fact that them giving Wilds' current singular elder dragon an MR upgrade being very very likely.
...though this is entirely just baseless wild(s) speculation, so take it with a grain of salt lol
(if we do get MR variants, I hope it serves as a fun alternative paralleling the upgrade tree instead of completly overtaking it like it is now, we got little hints of that now and before TU4 but it would be great if it was a bit more balanced)