Like said, Villeneuve and Zonta made a bet that they could take Eau Rouge flat out that year. Seeing the crashes that didn't work very well, but seeing the assumption that they could shows that around that year, cars could take Eau rouge flat out.
Since then, aero has become so much better. And even though less and less was allowed, the parts that were allowed became more and more refined.
If we then take Adrian's Newey quote;
The RB6 was Red Bull's 2010 challenger. Assuming 2000 to be the first year that cars could take Eau Rouge flat out, that means 10 years of aero development. In these ten years more and more have been outlawed and what was allowed has been refined and refined.
Since then, aero has continued to improve. Think of what effect the vortices shed by the front wing have. This was at it's early stages in 2010 and have since then been refined.
But that is assumptions, so let's compare qualifying times. What we have to remember is that in 2000 teams were allowed to change the whole car overnight, allowing an optimal qualifying as well as an optimal race setup;
2000: Mika Hakkinen 1:10.410
2014: Felipe Massa 1:08.759
As we can see from the Austrian GP, 2014 cars are quicker. What we also have to remember is that they are down on power and have more weight compared to 2000 cars.
Not enough? Let's take Canadian GP times;
2000: Michael Schumacher 1:18.439
2004: Ralf Schumacher 1:12.275
2014: Nico Rosberg 1:14.874
As we can see here, 2014 cars are significantly faster than 2000 cars, although a bit slower than 2004 cars. What we then have to take in consideration is that 2004 cars have a significant power advantage.
So with that said, we can see that 2014 cars are much quicker than the 2000 cars that could take Eau Rouge flat out or close to flat out.
2009 cars, which lost lots of downforce to 2008 cars took it flat out. I'd say it is safe to assume 2014 cars would be able to take Eau rouge flat out with ease.