Have xbox one, looking for the most cost effective console upgrade for GTA6

[kenmtb]

I am a casual gamer at best but I was hoping to play GTA6 in the future. Unfortunately it won't work on my xbox one.
Would it be best to get the x series after the game comes out or get an s series and try to upgrade it?
I would be happy if the performance and graphics were similar to GTA5 on my xbox one for a while after GTA6 came out.
Thanks