People who gamble are seeking risk. Why would they want to gamble in a pegged asset meant to reduce volatility?
BTS is about as risky an investment as you can get. We can expect people who are invested in BTS to gamble in similar percentages to Bitcoin. If they are only given BitAssets as an internal wagering option then...
Also BitAssets are just a currency option, currently a fairly risky one at that, BitAsset holders will often be trading speculatively & also be the exact same risky personalities who hold BTS, little reason to expect them to be much more averse or non gambling prone. (As nomoreheroes said above not much different to wagering fiat.) Even if we're talking 1/3 the rates, it's probably much bigger than anything else I can imagine.
Looking at the 2012 Bitcoin gambling report is probably our best 'bet'
http://www.forbes.com/sites/jonmatonis/2013/01/22/bitcoin-casinos-release-2012-earnings/(Bitcoin had a low user base & CAP through 2012 of about $70 million, so not too dissimilar.)
Satoshi dice had nearly 1.8 million BTC worth of volume and BitZino 700 000 BTC, so probably about $30 million dollars turnover. 2.5 million of the 9 million BTC would be about 700 million BTS worth of BitAsset volume & I think there were about 6 million betting transactions. Imagine just a fraction of that.
The most important thing is that a really low house edge, provably fair, funds accounted for on the blockchain option could not only satisfy gambling demand & bootstrap BitAsset use internally, but displace Bitcoin options which have recently been hit by a string of 'ponzi' take the money and runs...
Gambling is what made up half of Bitcoins volume and helped Bootstrap it and it still makes up the major chunk today. So nevermind BTS, it's possible that whoever takes the gambling even takes Bitcoin.