I'll point my miners wherever i get the biggest reward, (value as i define it) I'll MM anything of value, if my business is sustained by tx feed in a SC blocks, and the Bitcoin Block reward is not a significant income stream, I will have no incentive to mine it. the hashrate will grow on the chain that has the most value, I may even keep earning income on the SC and contribute to a coordinated attack to prevent people moving out of the profitable SC and into Bitcoin, note there would be an insignificant cost to me to do so, as I get my income from the SC.
The dynamics have changed since SC has enter the scene.
You are no more required to only mine one chain. You can simultaneously MM ANY chain that has considerable value and support the system has a whole. Creating a security hole in any of the interconnecting chains can be damageable to all of them you not only do you have economic incentive to mine all of them to secure different streams of revenue but as a miner you should also support most chains who gain any traction and community traction to secure the whole ecosystem.
I'll MM anything of value
In a SC scenario, there is no more only one chain with value. And growth in value of other, interconnected chains likely converge to all the other chains.
Of all the likely scenario, the death of the main chain because is the most far fetched one as it is the root for the whole system.
when you stop converting into the main chain and you have lots of other more valuable chains this is called inflation.
I'm still unsure where miners get there intensive to support a chain that docent provide a mining investment. when you can explain that you'll have me.