That's right. The only thing I would consider selling at the moment are altcoins forked from BTC, although you would also end up selling low to buy high, but since BTC is looking great as an investment for the future with possible Amazon acceptance and return of Chinese trading on the horizon that wouldn't be a bad idea.
ETH has still a chance to go up, like many other altcoins. I still hold some coins although they've been sluggish lately (LTC for instance).