So perhaps it is formal English, which has the problem. Judging your own manner of writing is understandably hard.
Anyway, the bold statement was intended to have the meaning:
"If ever in the future, some of the (honest - not intended to apply to premines such as Auroracoin or token coins with indeterminate supply and function) alts reaches even as low as 10-20% of BTC's marketcap, this is an indication that it has all that BTC has to offer and more, and will probably take over."
Well, this is an interesting statement, colloquial English aside.
A lot of the money in BTC is actually early adopters imo, perhaps even a majority, in a created wealth sense. Anyway, these early adopters have a bit of a wealth effect on their hands.
(Their at one time near worthless BTC's have now made them millionaires.) And where to put some of that? We have seen some very early brilliance from the likes of Erik Voorhees, imo.
Now, this is where it gets interesting. Those with the foresight to see BTC years ago is a rare thing. Black Swans are hard to spot, even when explained and handed to you (e.g. Just think of all the people who have heard of this space (from us) and do absolutely nothing. Some of whom might even ask you for investment advice 2 weeks after this talk but never bring up BTC! Hello, Hello, McFly). Anyway, so now these select few are looking for the next great step within and without this space. And imo, some have found it...
Something (or is that someone) tells me quite a few of them are looking here.