At the moment this thing is about the size of your standard Il-76, but I think with WS-20 engines we can see a stretched version like Il-76MF and give the much vaunted 65 ton payload that is as of yet unreachable.
Fortunately, Y-20 seems to have a significantly wider cargo hold/hull than Il-76 and is more akin to C-17 in that regard. If Y-20 can be stretched from its current 46.5m to an Il-76MF/C-17 class ~53m, PLA will get a very good strategic transporter that can compete with Il-476 in future, and potentially take a good portion of the market too, considering the next largest transporter would be the C-17 and that's going out of production soon if no one else orders it.
But for the foreseeable future, if XAC can only mass produce a Y-20 with baseline Il-76 performance, that would still be a massive leap for the PLA's airlift capacity. I'm just glad they had the foresight to make the hull very wide.