You guys are optimistic. I foresee there would still be the same amount of spamming, except that there would also be a lot of people asking why their activity is not increasing.
There wouldn't. People would be unable to farm accounts to higher 'levels' in these sections anymore. There are two likely outcomes:
1) They stop posting.
2) They try spamming other sections.
With the second case it will be easier to detect as contributing to other sections is significantly harder (i.e. you have to put in more time for a decent post).