They can move the World Cup, but I assume there would be heavy penalties involved and I doubt that they are even considering it.
I would really like for World Cup to be distanced from politics and topics like these but in reality I think we will have hard Covid rules, with some important players missing because they will not want to get the vaccine. Hope I'm wrong though.
I strongly doubt that Qatar's opinion is interesting to anyone and it will be allowed to impose it. It is clear that countries have sovereignty and can set their own rules on their territory and not give permission to enter those who do not agree with them, but if at least a few major players boycott the World Cup because of the issue of vaccinations, it will be a huge blow to everything football.