It is a good news, but only for ETC holders. I do not believe that it will have any impact on ETH price
and overall Crypto market. It is just a coin added to one of the biggest exchanges.
ETC is a forked coin from ETH, has different blockchain, different community base and there's nothing to worry about, even if it gets listed into some major exchanges. It may affects ETH, however that's only a little bit.
The fact that coinbase adding ETC is just as normal as when other exchanges adds more crypto to its listings. Its main point is to cover a wider range of cryptocurrency users.