I only currently have a G43, not a 43X nor a 48.
It's my understanding that Tom at Dark Star Gear (my favorite holster maker) makes his G43 holsters sized longer than needed with empty space past the muzzle. This was done before the announcement of the G48 and for the purpose of having a little extra depth to prevent the holstered gun from flipping forward around the waistline. Similar theory in Tom's newest mag pouches that go an extra inch or so deeper than needed and utilize a little spacer to prevent the mag from getting inserted too deep inside.
I believe Tom's G43 holsters will hold the G48. Given the holster is the same length, I don't see why I'd choose to run a G43X over a G48 if I was using my Dark Star Gear holster. It would feel identical. So I'd either need to get a shorter holster that was sized exactly to the length of the G43x or just run a G48.
Tom strikes me as a brilliant engineer who has taken training with top men (top... men) so if he added an extra little bit past the muzzle on the G43 holster, I suspect there's a really good reason for that. I'd like to hear Tom weigh in on this because if it's not desirable to have a G43x holster be smaller than a G48 holster, then it negates the desire for me to have a G43x. I think Tony Mayer makes holsters that are just as good as Tom, but I don't own any so I'm not sure if Tony gives a little extra empty space beyond the muzzle on G43/43X holsters.