My opinion is that Redbull is working on 80% for 2020 car and 20% on RB15. Lack of updates that address rear instability and the fact that Marco has confirmed Gasly will finish the season makes me think this way. I think the problem with RB15 dont have easy solution. Still remember Newey's face at Bahrain pitwall and gestures they changed with Horner.
The other that bothers me is Honda progress. Actually PU don't look so bad in race pace. They lack max power and potency but as Wazari said they push in engine efficiency and race performance and they achieve their goals. I think that with expected Sochi update they will fill the power hole and quali modes and actually now remember Wazari's words from recent years that this is not so hard to achieve if you have stable and efficient engine. At the end - 2019 tyres created so many problems...