I would suggest updating .nuget\nuget.exe with this command from the command line:
nuget.exe update -self
[EDIT] : Close VS Solution first. If there’s an update and the solution is opened, nuget.exe will be removed from the solution.
You could automatically update nuget.exe on restore by modifying the .nuget\nuget.targets to add the above command. I’d look at the restore command in there as an example. But I’m not sure if it’s worth it, nuget.exe updates aren’t that common, and backward compatibility should break very rarely.