The magnitude of the change is bigger than in 1974 but the Dems will have fewer seats than they did at the start of 1975. In 1974, they gained 4 Senate seats, leaving them with 61 total. In 2027, they will have 54-56 senate seats.

Kansas, Iowa, North Carolina, South Carolina, and Alaska all have Republican Senate seats up for reelection in 2028. All five of those states also had Republican Senate seats up for reelection this year and the first four at least, and possibly the fifth, have flipped from red to blue. If 2028 goes like 2026 and Alaska and Mississippi flip this year, Dems will have 61 seats in 2028, enough to break the filibuster for contentious votes along party lines. In terms of the end result of the makeup of the Senate, 2026 is more like 1972 election in which the Dems had 56 seats after the election and 2028 may be more like 1974 depending on how optimistic you are.

Shout out to Wikipedia for documenting all of this.