Bitcoin only and no altcoins until after the fork next May.

I see Bitcoin dominance reaching 90% as most of the alts are quite useless and scams.
Alt coins will go down a lot more.

I doubt there will be an altcoin season again. If this happens it should be after the halving.
Also I wouldn't touch most of the altcoins that pumped in 2017. Most of them are dead already. They will pump in an altseason but they won't give you the returns you would expect.