WTF in 30 years the block reward will be 0.10 BTC per block. it costs a minimum of $3300 to make one today.
do you know what the price of bitcoin will be? - I dont, but given the existing reward structure I know it will be as impervious to a 51% stack as it is today, change the prototypical intensive and I'm not so sure.  

If there are no SC and Bitcoin needed to support the same security it has today the price of a a single bitcoin would have to sell for over $30,000 just to maintain the hashing power we have today - that assuming no growth, if there is big growth, and we talking trillions in market cap, a block reward will have to be higher, can you guarantee there will be enough hashing power to protect Bitcoin if miners get most of there revenue from another chain?