The segwit softfork may fix some things that make side chains more feasible, but that undersells it severely. It mainly solves a bug in bitcoin that prevents a good implementation of Lightning Network (which is not a side chain), and it also upgrades on-chain transaction capacity by doubling it, while solving another bug in Bitcoin (quadratic scaling of sigops) which make such a capacity increase safer.
More information here: https://bitcoincore.org/en/2016/01/26/segwit-benefits/