I looked at the last 4-5 years on btc vs SP500 and it looks like they are getting more in-tune, plus btc swings vs SP500 are abating.
All data from Dec 31 prior year to Dec 31 next year:

2015-2016  SP500 +9.5%
2016-2017  SP500 +19.4%
2017-2018  SP500 -6.2%
2018-today SP500 +29%

vs

2015-2016  BTC +123.6%
2016-2017  BTC +1368.5%
2017-2018  BTC -73.6%
2018-today BTC +96%

It looks to me that we simply amplify (in the last 4-5 years) the SP500 move.
Judging by the prior statistics, after at least 20% move (yearly) in SP500, there is at least one more consequently positive SP500 year.

Prediction: we would roughly triple or quadruple SP500 gain in 2020.
7-10% gain in SP500 would result in about 30% gain in BTC, therefore the target for BTC next year (12/31/2020) is about 10K+/-1K (9k-11K range).