Then again, Star Trek is clearly an alternate timeline, and the DY-100 could've only been the very beginning of a spanning space industrial development.
Or even the midpoint of an already highly profitable business. But the timeline also allows it all to come crashing down well before WWIII. Perhaps the Eugenics Wars themselves resulted in near-total loss of space assets; perhaps subsequent international squabbling did (it being simpler to evict the United States or China from Mars than from Earth, say, and certainly tempting strategically and symbolically).
Mankind's presence in the solar system might be dictated less by advances in technology and more by the ebb and flow of politics and economics, just like seaborne exploration and exploitation was in the 1500s. There could be more colonies in 1990 than in 2010, say, and a better connectivity to Mars in 2000 than in 2030. But the underlying fact would be that the (re-)establishing of presence would have been possible since the 1990s already, and might happen at the drop of a hat at any later date.
Timo Saloniemi