I just got off the phone with someone at GoDaddy. They say that over 900 new extensions will be rolling out within the next year or so...
http://www.godaddy.com/tlds/gtld.aspx?ci=85337
The belief here is that over time, internet extensions will help categorize/compartmentalize the web, to make searches more relevant.
Content will be just as important, so if you were to register tits.construction (for example), it will likely NOT make any sense, as you will be in a category that was intended for construction-related businesses, so your ranking will likely suck, as it is not in sync with the intended purpose.
Network Solutions just rolled out 45 of the upcoming 900+ but more are on the way. A few of these 45 are currently exclusive to Network Solutions, but not all of them, and once it all shakes up, they will likely ALL be available through ALL registrars.
ALL domain names are slated to go up in cost in the near future, with an average annual cost to be around $20 or so, to include .com and other extensions that currently exist, so if you have a number of names that you want to use for years to come, and you can afford to extend them for 10 years at today's best rates, it may make sense to do so.
Anyway, that's all the info I've been able to get so far.
If you learn more, please add it here for all of the GFY peeps!