Actually bitcoin is taking a lead again and alts begin to fall down.
I'm a long-term holder, so I keep my alts nevertheless. Each market has its cycles so I'm pretty confident with my investments.

I can definitely see more growth for altcoins than for bitcoin. BTC has had awesome 2017, it still can go up to 40K even but it will be 2x at most. Alts can go 10x-50x in valuation. Ultimately you can always transform your alts into bitcoin, so that's why I think holding alts is good approach.