Bitcoin is great for this but it's not stable so for me it's not a good idea despite the fact that it has potential of rise and profit.
I am looking for very stable altcoin and of course a little popular to get rid of coin die.
Hmm.. in my eyes this doesn't make sense.
Let me explain. Usually Bitcoin is unstable and the altcoins are even more unstable. So finding a stable altcoin sounds .. strange.
Now, my advise would be to diversify. Get Bitcoin and a couple of altcoins too. Some will rise, some will fall, but overall they should compensate each other.
With some luck you'll have a rich retirement.