Yes no doubt bitcoin now is at low price but with the passage of time it will be high. We know altcoins are also good to invest but it never give profit better than bitcoin. We know bitcoin is at demand now a day so its not good to exchange your bitcoin into Alt coins. Altcoin are in ETH and Ripple but I prefer to keep my bitcoin saved instead of changing them.
I think you need to check your facts there have been many instances in which altcoins in general have outperformed bitcoin, just because it is not happening in a consistent basis anymore it does not mean that it cannot happen in the future, at those times it is wise to exchange your bitcoin to altcoins and enjoy your profits, just do not forget to get back to bitcoin because that growth never lasts and at some point bitcoin reverses the situation and begins to grow way faster than altcoins.