The concept of Unlimited gTLDs could just as easily it could fall flat on it's face, though. It's entirely possible that keyword.keyword is just too 'bizarre' for the .com conditioned public and they reject it. If not, though, Katie Bar The Door. The same power we all recognize as being inherent to keywords will suddenly be shifted to the right of the dot and premium .com names will devalue in direct proportion to the cost and availability of an eponymous TLD. We're in uncertain times.
Let's face it, that is the most likely outcome rather than it being a 50:50 bet.
One thing that's VERY important to note here is that what we're seeing with "build-your-own" TLD's is a universe away from what we saw in the past with stupid gTLD's like .biz, .asia, .pro and .info. It's a complete failure of logic to cite other lame ICANN fabricated gTLD's as being some sort of harbinger for the pending failure of completely custom TLD's. That's comparing a Yugo to a Ferrari and claiming them to be equal since they both have four wheels and an engine. Your own TLD is a very special form of self/business-actualization that is incomparable to simply buying a keyword on a generic 'special purpose' gTLD platform.
While it's 100% dead-certain that acquiring a TLD will only get cheaper over time, it's equally certain that the associated costs won't ever get all the way down to the domain name level, where the only barrier to entry is a few bucks and a debit card. You won't see guys in the 3rd World snapping up TLD's from internet cafes, before going home to their mud and twig huts.
Still, unlimited gTLD's is very very very interesting; people in the domain community are generally sticking their fingers in their ears and shouting "LALALALALA" rather than making a cool analysis of what might happen. Of course, based on what drop lists look like, I'm convinced the "domain community" is filled with idiots to begin with, which is a beautiful thing. Wherever idiots with money are found, there is profit to be had :D
Let's face it, everytime it is totally different and better otherwise nobody would buy the "new relovutionary change".
Going back in time,
1999: .cc and .ws - All the rage amoung new speculators was .cc, .ws and .tv - they were going to be serious competition for .com.
2000: new.net - this was different because of all these new extensions, .shop, .travel etc. ISP's were adopting this alternate route it and it was bound to take off and give serious competition to Icann. Indeed Icann was probably going to have to add all these extensions to the dns eventually. They'd have no choice if they wanted to stay relevant.
2001: .info and .biz - supposedly it would be different this time, these were the real deal, not lame repackaged country code extensions or alternate DNS names.
2002: .us This is the first real challenge to .com. Cctlds are the main extension in many countries around the world. How could this not get popular?
2006: .mobi - This is totally different! the first extension specific to the mobile web, this was bound to fly. It was totally unlike prior dud extensions (.info, .biz) in that it had a genuine rapidly expanding market and was back by the biggest Internet co's, Google, Microsoft etc, how could that ever fail?
Today: all the new extensions - It is totally different this time, unlimited new tlds, the world could easily change, get your credit cards ready!
Whilst alot of new players get involved in these you also see some people constantly make the same mistakes. I remember alot of new.net people going mad for .biz and .info and alot of them liked .us and then .mobi aswell. Every time it was going to be different.
My prediction is these names will be another repreat of the past, totally different, yet some somehow totally the same with much the same types of people investing (those who missed out perviously). It is a new set of extensions designed for selling "the dream" to domainers, it will be marketed mainly to domainers and cared about mainly by domainers. It will have a negative effect on .com, but only due to small numbers of co's using them, just like .cc, .tv, .info and .mobi.