Segwit2x branched off the Bitcoin Core 0.14 release and has a diff of less than 500 lines as of this writing from Bitcoin Core 0.14. About half are related to BIP91 (orphan blocks that don’t signal Segwit) and the rest is split between testnet5 (new testnet), change of name (Bitcoin Core => Segwit2x) and BIP102 (2MB Blocks). It’s within the realm of possibility that this code can get merged into Core, for example.
The hope of Segwit2x is that the hard fork changes would simply be accepted into Bitcoin Core. Of course, some signers of the New York Agreement have explicitly stated they don’t want Core to control the reference client, so this is an open question.
Let me know in the comments below.