Its been passed around on TWiV and immunologist twitter awhile back that there's ~20 different epitopes on the spike protein that would need to mutate in order to achieve immune escape.
The read on that is that immune escape should come at a cost to fitness and less virulence and transmissibility. The virus will have to "pay" with fitness in order to buy stealth.
At the same time though there have very obviously been multiple different mutations on the spike protein which have enhanced binding / viral load / transmissibility / virulence. So the virus clearly has some room to maneuver in that space.
The read on that is that immune escape should come at a cost to fitness and less virulence and transmissibility. The virus will have to "pay" with fitness in order to buy stealth.
At the same time though there have very obviously been multiple different mutations on the spike protein which have enhanced binding / viral load / transmissibility / virulence. So the virus clearly has some room to maneuver in that space.