I don't think there is a problem if buterin will leave ethereum, I'm sure ethereum will be able to last a long time in the future, no doubt about ethereum because this coin has the advantage that it will remain a strong and long-lasting coin in this cryptocurrency
There is a huge problem. Seeing the icon and founder leaving his creation, some people think that there is something wrong with his creation that he cannot fix. Anyway, that was just an assumption. If ever Vitalik left ETH, lets just hope it won't have a huge impact on the project and the token revolves around it.