Vega 11 would, all things being equal, be an upgrade over Vega 8.
But it's also:
GloFo 12nm vs TSMC 7nm,
DDR4-2400 or 2666 vs DDR4-3200 or LPDDR4X 3733+
1100MHz at best (power limited, even at 25W TDP) vs ~1500MHz at 15W.
Claimed architectural tweaks (I doubt these are significant though).