I'd say Ethereum because it has had its own fork now and the price can be expected to rise. It is likely that a lot of altcoins will rise as people move money back out of bitcoin.
This can happen, yes. Bitcoin is in up and after a few time, like always, there will be hard fork for bitcoins and they will go down. But for now, as the bitcoins are so much high, the altcoins are not in good mode of prices. Reason is one and you know it, the reciprocal. So in upcoming days when bitcoins will be in dip, altcoin rises and that is the time for them to sell, keep them now.