Going with your Clinton/DEM Senate assumptions, that will last only two years, with 25 DEMs up for reelection in 2018 compared to only 8 GOPs. I count at least 5 Red DEM Senators and 7 Purple DEM Senators up in this mid-term where DEMs are historically election-challenged.
Four of those DEMs, from RED states, crossed over on yesterday's amendments at least once, Donnelly from IN twice. Heitkamp from ND, who crossed once, also voted with the GOP to filibuster Toomey/Manchin in 2013, as soon as she took office, playing her 'long game' against future anticipated NRA ads.
Clinton will get her 9th Justice, by your assumptions, after Schumer pulls the nuclear trigger. You may see Ginsburg leave on her own free will during this 2-year span. Once the GOP takes over in 2019, Clinton will get no more Justices, as with the current McConnell/Grassley gambit.
GOPs still have their 'long game' of 2010 in place for 2020, dominating state legislative elections. DEMs and their DNC Chief at the time, Sen. Kaine of VA, still haven't figured out what hit them. After two years of Clinton batting the GOP in Congress, I expect another mid-term drubbing of the DEMs as we saw in 2010 and 2014, with the NRA certainly playing an active role, which is their legal right .