The transparent market right now (which are all non-anonymous coins) is ~7bn USD.

The anonymous market is ~ 10 mn USD.

If 1-10% of the transparent market moves to the private/anonymous market, we are talking about 70-700mn USD for all anonymous coins.

This "pie" is too large for a single coin to own it. In fact it would be unhealthy to do so. Therefore multiple coins can co-exist in this 70-700mn market cap and benefit from it (by multiplying their price and marketcap), all the while competing to make the best anonymous solution (which, again, is quite healthy).

Clones aren't much of an issue though because a) they are not innovating b) their price barrier will always be dictated by the "why should I invest in this clonecoin instead of the original?" factor... and the more clones there are, the better it is for the original coin - as the market is saturated with clones.

Btw, Darkcoin is not only about privacy: It's really a bleeding edge coin / a development platform for new stuff - and I predict a bumpy ride due to this issue alone, as much stuff will need patching as it goes along. I believe there will be issues with future functionality as some of the things are totally new and have the potential for quite a few bugs to resolve, like the 10% payment, in a proof of stake/proof of service way, towards the masternodes. We might even see fork failures. Bleeding edge, is bleeding edge - so one must be ready for everything... Personally I'd take bleeding edge any day over a shitcoin - and so far it's paying out handsomely despite whatever issues have appeared and been resolved so far.

Regarding future development, the Dev is commited* to bring new features in the long run, including more anonymity features + mainstream features. He hinted of a killer mainstream feature after he finishes with DarkSend. We'll see how that goes.

* As a full time job for the next 2 years.