BTC's network value is almost too large to fail at this point.  There is so much investment in BTC that if it fails, all crypto will fail with it.  What I would like to see from Sidechains is the ability to 2-way peg current alts to block chain.  I think Blockstream should employ someone who's sole purpose is to help Alt's peg to BTC via Sidechain.  Imagine having the functionality of Alt's tied to BTC blockchain.  Anyway, I'm very excited about Sidechains.