So back to the OP, I should have stated this:
Altcoins, in the OPs intention, are only created by hardforks. Softforks can't make altcoins two surviving chains.
SegWit would only be an "altcoin" if there was a hardfork with two surviving chains. and segwit was minority
whereby BU and a flock of other implementations of consensus (classic, xt, and other adjustable blocksize PEER imps) become bitcoin
due to having majority of hash, nodes and merchant acceptance
core could kill off its minority chain and then just add a few lines to be dynamic and join the PEER network of many implementation
BU would only be an "altcoin" if there was a hardfork with two surviving chains. and BU was minority
whereby segwit and a flock of other implementations of consensus (classic, xt, and other imps running as downstream second TIER) become bitcoin
due to having majority of hash, nodes and merchant acceptance
BU could kill off its minority chain without any code changes can just join segwit as a downstream second tier of many implementations
i removed this line:
If BU survives and the minority chain dies off, BU transforms from altcoin into "Bitcoin".because if BU had majority. its already bitcoin along with the other implementations (where segwit is the altcoin or just dead)
theres still some irregularities even with the FTFY summary. due to when/if core triggers their bip9/UASF/PoW change, and which markets treat it as such.
but its close enough
I just revised as you commented, see my revision.
I do not agree. I think an altcoin is always an altcoin until there is one chain.
If there is a bilateral split, the spiting chain will always be an altcoin since that
breaks the Consensus Mechanisms.
So, if both chains survive in a non-bilateral situation, the determination of altcoin
status can not be determined. I think one must die to truly determine who is
the "Bitcoin". If an implementation wishes to be the "new protocol" the old must
die, it can not be "the most hash currently". It must be finalized in general and
for the economies.