You act as if the infrastructure built around bitcoin couldn't be adapted to BTSX very quickly. Here is the little secret that gives BTSX an edge: it works at almost any scale.
Regardless of BTSX market cap users can settle and contract in dollars, gold, silver, etc while getting a higher yield than their bank. At the end of the day BTSX produces real value while BTC consumes real value. BTC network effect is based upon people building infrastructure around BTC hoping to make money in this industry. Their infrastructure becomes more valuable with BTSX and thus they will support it.
Actually I think it takes quite a bit of time and expense to integrate new cryptocoins into existing Bitcoin infrastructure. Especially making sure you've done so securely. Security is expensive. The big players will not want to invest in adding a new altcoin unless they see that it has staying power and that it is going to become very widespread.
Also a lot of the big players do not see an advantage to it in terms of increasing the value of their infrastructure. To them the challenge of cryptocurrencies is to make it dead simple and easy for everyday people to use it. Reducing mental overhead is of absolutely paramount importance. Adding choices for multiple different cryptocurrencies is in itself enough to confuse people and drive them away. That is part of why the likes of Bitpay etc., are not jumping on the altcoin bandwagon. They see more advantage to their infrastructure from one successful currency with extensive penetration than with dozens of competing currencies, each with partial penetration.
Also, this gets to one of Bitshares most obvious weaknesses, which partly has to do with how new it is. The mental overhead is way way way too high. There is drastically too much to learn to get started and feel that you have a grasp of how to use it. The client is way too complicated. And there is too much redefining of terminology that really doesn't need to be redefined. Making people learn complicated new terminology imposes mental overhead and retards adoption. The client can obviously be streamlined with time (or alternatives be offered). But the community doesn't seem to get how all the new terminology, which is really unnecessary, is seriously hurting them. If you just said "BitShares is a new cryptocoin that is nearly instant, more secure, less wasteful, more anonymous, more decentralized, and where you can peg value to any currency or asset you like" that would be a lot more effective than talking about multiple "decentralized autonomous corporations", "crypto equities", "bank and exchange", etc. All this attempt at changing the paradigm gets little and costs a lot.
I think it's possible to get some of the infrastructure to support a coin technology like Bitshares, but it won't be easy either for the providers of the infrastructure or for Bitshares to convince them.