2018 US Senate Election-maximum number of seats Democrats can have after 2018.

[nkpolitics1212]

Democrats win
HI-Hirono-D 24D unopposed
VT-Sanders-I/D 25D No Republican challenger
WA-Cantwell-D 26D No Republican challenger
CA-Feinstein-D vs. DeLeon-D 27D 2 Democrats facing each other in November
NY-Gillibrand-D 28D
RI-Whitehouse-D 29D
DE-Carper-D 30D
MN-Klobuchar-D 31D
MA-Warren-D 32D
MD-Cardin-D 33D
CT-Murphy-D 34D
NM-Heinrich-D 35D
NJ-Democratic Primary Winner-D 36D
MI-Stabenow-D 37D
VA-Kaine-D 38D
ME-King-I/D 39D
PA-Casey-D 40D
WI-Baldwin-D 41D
MT-Tester-D 42D
MN-Smith-D 43D
OH-Brown-D 44D
ND-Heitkamp-D 45D
FL-Nelson-D 46D assuming Scott-R is the Republican Nominee.
WV-Manchin-D 47D
NV-Rosen-D 48D
AZ-Sinema-D 49D
IN-Donnelly-D 50D
MO-McCaskill-D 51D
TN-Bredensen-D 52D
TX-O'Rourke-D 53D
If there are 2018 special election in AZ-Kelly-D 54D

[Tiggeroshii]

1. 57 is a realistic number next year if trend keeps up

That is, they could win all seats up for election

[nkpolitics1212]

2. 57 Democratic US Senate Seats would mean Democrats have to win MS,NE,UT,and WY.

MS-Wicker-R has to lose in the Republican Primary to Chris McDaniel-R. Democrats have to nominate Brandon Presley-D.
NE-Fischer-R has to lose in the Republican Primary. Raybould-D will have to win big in NE-1CD(Lincoln Metro Area) and NE-2CD(Omaha Metro Area)
UT-Evan McMullin-I has to run splitting the Republican vote allowing Wilson-D to win with a plurality of vote.
WY-Barrasso-R has to lose in the Republican Primary to Erik Prince-R. Trauner-D will have to remind WY voters about Prince's shenanigans.
2020 could give Democrats 60 seats if Democrats hold onto AL-Jones-D(Tossup), MI-Peters-D(Lean Democratic),MN-Smith-D(Lean Democratic),NH-Shaheen-D(Lean Democratic) and VA-Warner-D(Lean Democratic) plus pick up
AZ in either 2018 or 2020 Special Election. Republicans will nominate an Arpaio type candidate.
CO-Hickenlooper-D or Perlmutter-D will defeat Gardner-R by a double digit margin.
MT-Bullock-D will turn MT into a Tossup.

[Tiggeroshii]

3. Yeah

...if trend keeps up

Generic congressional ballot dems +20-25 would do the trick.

That would also probably translate to a good 300+ congressional seats