That's a common misconception. Tax levels are the highest they have ever been in since the 1950's, when we were paying for a war, it's just that a lot of the tax burden is stealth taxes. Overall, the tax take is about average for a developed country. There isn't a huge scope for an overall increase in taxation as a % of GDP.
Once this is all over, the country will be potentially bankrupt; unable to borrow any more and unable to ramp up taxes without adversely affecting consumer spending and thus the economy. Severe austerity, and by that I mean actual austerity like that which they had in Greece, is a possibility irrespective of whoever is in charge. It isn't going to be fun.