That's an interesting thought. I wonder how people will value those sidechain tokens in the exchanges then. To my understanding, in order to receive tokens in the sidechain, a certain amount of BTC must be locked. How many tokens would that be would depend on the developers I think. So if 1 BTC = 10 RSK, then I think that would be a constant. So if RSK is listed in an exchange the fair price would always be 1 BTC = 10 RSK, but BTC's fiat value always changes. I think that would play a role in the changes of the value of RSK too. But bottom line you will receive 1 BTC back to the main chain if you have 10 RSK.
What I asumed is that since it's a one way pegged mechanism or sorts, then the ratio of price is always 1:1, so this means that it does not make sense to have an exchange for this... im not sure how this works anyway so im just asking.
I like the altcoin speculation aspect and making money on the altcoin markets it's fun, so it would suck if altcoins stop existing due sidechains making all of them irrelevant.