If you inductionally apply the argument that you shouldn't increase taxes because someplace else offers a lower tax burden, no place can raise it's taxes. There are other factors in choosing your country of residence (and nationality) than taxes.
A wealth tax of 2-3% would enormous. Combined with an average capital gains tax, the incentive to get the capital out of the US becomes huge. Yet, even 2-3% doesn't bring in that much money relative to deficit spending and stimulus bills, so who is to say it's going to stop there? If you're clueless enough to go with a 2-3% wealth tax, you're clueless enough to go with 5% and more (Warren).