However, I'm not sure how far Bitcoin will go, will they continue to update the source code when proof of work becomes completely obsolete? Will Bitcoin instead migrate to a different consensus algorithm, if it's even possible?
PoW only becomes outdated if something better comes along. that hasn't happened. maybe it could, but it'd have to be an incredible concept.
(that's like the dictionary definition of "outdated" btw, "something better comes along")