Yes it was almost G'Kar / Londo in their final embrace.
I've gone back and watched "The End of Time, Pt 2" ... and there seems little doubt that the character played by Timothy Dalton is indeed Rassilon. But then I don't know anything about the character prior to nuWho. According to a Wiki article "there are many contradictory legends about Rassilon. " That alone can foment some of the theory that Dalton played someone else. But then much of those contradictions occurred before TEOT. That tilts things back to this probably being THE Rassilon.
But for me the final proof is that is the name in the credits. And we all know that television is the Supreme Authority over all we are.