I still think that MyEtherWallet is way better when it comes to storing and managing your Ethereum. Even though Coinbase is a huge company, I don't think that it will affect popularity of tokens a lot. Support of ERC20 tokens isn't as important as supporting SegWit. There are so many tokens that there is no point in assuming that their price will increase thanks to these news. Coinbase has started expanding lately, why so suddenly? Is it because they acquired license in the United Kingdom?
They are expanding, because there is demand for it. They don't have to support all of them, but however some people find it hard to use MEW for instance, of asking themselves if they backed up everything right and if they did it in secure way. Some people don't want to try etheredelta or IDEX, no matter if they are decentralized exchanges. Some people won't think into buying if their exchange doens't support it and coins usually pump after they are added to coinbase.