Fallout: New Vegas Story Quest questions?

On Fallout: New Vegas, I have completely messed up Caesar's Legion, and have help Dr. House up to point where he has upgraded Protectrons. I wan't to help the NCR now, and I believe I'm currently trying to get the Boomers to help the NCR. Is it still not to late to betray Dr. House (buy killing his true form) and help the Boomers to help the NCR?