I don't believe that alts days are coming, alts may grow slightly, but it's better to invest most of the money in Bitcoin now and distribute the rest in equal parts in alts.
You can invest your money in Bitcoin and Altcoin simultaneously,
if you have $ 1000, then you buy $ 500 with Bitcoin and $ 500 you buy Altcoin, and hold

It all depends on individual knowledge in terms of making a profitable investment in the market but invest all in Bitcoin is the best option for newbies while an experienced investor or trader can go for both Bitcoin and altcoin.