The collapse may last for at least Q2-Q4 2019, or it may take even more, but it doesn't necessarily mean the market will go down essentially compared to where it's now. $3000 is a good option to buy with a goal of 3-5 years.
I don't believe that Bitcoins will collapse going ahead in 2019, we're on the cusp of a bitcoin rally it's only a matter of few days. The bottoming in bitcoins has ended, and now it's finding strong resistance at 3600$ levels, some more push and we'll reclaim 5k levels. If you're not aware then do note, that Bakkt and Nasdaq bitcoins futures are launching in Q1 of 2019, which shall send bitcoins prices soaring to the moon.