It's not like the closure of a chain resturaunts where an entreprenuer can go out and get the funding for a place of business and stuff to cook with. Creating a car manufactoring company is in internet speak "serious business" with massive outlays of capital and the potential for very long run losses as you enter a global market against other companies that provide huge benefits to larger manufactorers.
So sure...in 10 or 20 years a up starter may try to step in and make a niche but the most likely result would be the market share gobbled up by established companies which equals less competition.
Also...the origional bailout obviously did work. GM is still a strong company with lots of assets set aside to weather any rough patches due to the macro economic climate.