Not only are there more people today than in von Neumann's time, but it is far easier to be discovered or to educate yourself. The general prosperity level of the world is also far higher. As a result, I expect, purely on statistical grounds, that there would be far more von Neumann level people today than in von Neumann's time. I certainly don't see a shortage of brilliant people in academia, for instance.
What is a test for a von Neumann level intelligence? Do you think "top people" in technical fields today would fail?
My intuition says that if we took the 10000 most intelligent people in the world, put them together and told them to work on some technical project, that would be much less effective than if we could make 10000 copies of the most intelligent person, in part because the 10000th most intelligent person is much less productive than the 1st. As evidence for this, I note that there are very few people whose "known for" list on Wikipedia is nearly as long as von Neumann's, and you'd expect more such people if the productivity difference between the 1st...
I'm skeptical about trying to build FAI, but not about trying to influence the Singularity in a positive direction. Some people may be skeptical even of the latter because they don't think the possibility of an intelligence explosion is a very likely one. I suggest that even if intelligence explosion turns out to be impossible, we can still reach a positive Singularity by building what I'll call "modest superintelligences", that is, superintelligent entities, capable of taking over the universe and preventing existential risks and Malthusian outcomes, whose construction does not require fast recursive self-improvement or other questionable assumptions about the nature of intelligence. This helps to establish a lower bound on the benefits of an organization that aims to strategically influence the outcome of the Singularity.
(To recall what the actual von Neumann, who we might call MSI-0, accomplished, open his Wikipedia page and scroll through the "known for" sidebar.)
Building a MSI-1 seems to require a total cost on the order of $100 billion (assuming $10 million for each clone), which is comparable to the Apollo project, and about 0.25% of the annual Gross World Product. (For further comparison, note that Apple has a market capitalization of $561 billion, and annual profit of $25 billion.) In exchange for that cost, any nation that undertakes the project has a reasonable chance of obtaining an insurmountable lead in whatever technologies end up driving the Singularity, and with that a large measure of control over its outcome. If no better strategic options come along, lobbying a government to build MSI-1 and/or influencing its design and aims seems to be the least that a Singularitarian organization could do.