Mercedes did bring updates to Sochi other than aero. Although there is not much specific info on PU revisions. I'm not sure they would hold back after Sunday. Even with the WDC, and WCC locked up IMO Toto will want to display dominance right up to Abu Dhabi. He will do "anything" to ensure Lewis has the opportunity to win every race until the end. The expression on his face at Bottas on Pole tells the "Toto Tale." Toto would crap on Bottas in a heartbeat to give Lewis a win. But that's just my opinion. I'm a Mercedes and Hamilton Hater so it's hard to be objective with them.
I also think Ferrari could have the pace, but they really seem to be lost at the moment. IMO, the situation around Kimi and the will he stay or will he go drama has caused them to loose a step that they have not been able to regain. I just don't see them working as a Team as well as Mercedes at this point. There are most likely no more updates coming for Ferrari the remainder of 2018 as well. Ferrari may find themselves in a similar position in 2019 with Leclerc and Vettel. I'm concerned about the chemistry with Vettel. I think Leclerc will be a formidable challenge in 2019 if he has the tools.