Bitcoin still has a lot of potential for growth, but there's little need to hold it directly, since all other cryptos are linked in price and will go up or down against the dollar, with it.
Honesty, I wouldn't hold any of the current crop of cryptos long. Some are innovative and are attractive to miners, but none really have anything more to offer regular consumers and to differentiate themselves from the rest. The only one to hold some real promise of going big is Dogecoin, and that's really on hype and publicity alone (but hype and publicity may really be all it takes). Obviously it won't go as big as BTC due to the supply and the fact that it's inflationary. There's also a lot of people holding a lot of Doge who are ready to sell the moment the price creeps up, which is really holding the price down.
At the moment, there's a lot of good money to be made by keeping your finger on the pulse and riding the waves of various altcoins up and down. There are lots of peaks and troughs, and more money to be made buying low and selling high, then rebuying when the price drops again.
Personally, I think that the open source model will be a problem for cryptos, as any innovation can be immediately cloned, effectively increasing supply. How can even an innovative coin truly take off and grow when it can spawn 1000 alt-coins the next day? I have a feeling that the next real Bitcoin successor will be truly innovative, and not be open source.