I personally think it is a good idea, but you also need to be aware that in this altcoin economy everything it is possible and it would not be so unlikely to see an eventual drop in the bitcoin price, however most analyst are totally convinced that the price of bitcoin is undervalued and sooner rather than later it will hit the barrier of $1000 again, so it is undoubtedly a good long term investment.
But bitcoin is not an altcoin, bitcoin is the best cryptocurrency, bitcoin is the coin to have, the envy of every single altcoin in existence.
Offcourse bitcoin is not just an altcoin. Bitcoin is the real deal. And maybe 1 altcoin will grow very large, but bitcoin will always be the first and best of all no altcoin will ever be able to have such a large eco system. We should be happy that bitcoin nowadays is growing and growing.