If Johnson can't vote, it's actually 49 Republicans, 48 Dems, 2 Independants. We would hold a one seat majority over the Dems.
Unfortunately, the two "independants" would vote for a RAT leader, and thus the party in the minority would control the Senate. I hope all the Joe Lieberman worshippers on FR are happy they donated time and money to keep his butt in office instead of Talent/Allen/Burns, etc.
Though I do think if Johnson's condition doesn't improve, the Dems would have a MINO (Majority In Name Only). They'd technically run all the committees and have all the leadership positions, but if any Dem is absent at any given time, 49-49 votes would be broken by Dick Cheney.
I would love to see Cheney poised to do the same. The Rats will feel terribly oppressed and obligated to stay close to prevent votes where Cheney might step in.