Obvious

The private companies will take the money and after it has been
spent they will discover that... (Oh wonder) they can't deliver
anything because they lacked the expertise and funds to redo what
NASA did during all those decades of development.

Since the U.S. economy will be in a far worst state than now,
the question of rebuilding NASA will not even be posed. Expertise
will be already lost, the industrial tissue that made human
space travel posible will be gone.

At that time, other nations will be travelling to the moon.
This is not the end of manned space exploration, just the
end of american manned space exploration.

We can discuss this again in 2015.

P.S. I remember all those republicans crying in this newsgroup
all these years:

DESTROY NASA!
JUST PRIVATE COMPANIES SHOULD DO SPACE TRAVEL

They are well served now.