Yes.

For the ordinary user, SegWit is backwards compatible.  It needs a majority of the hashrate to avoid a chain split, but by default it doesn't cause one (as I understand it).  Therefore it would be an upgrade of Bitcoin with a consensus, and if in the future there was a split that separates from consensus that was agreed before, that one would be the "new coin" to put it that way.

Feel free to correct me on that but I'm pretty sure that I can call it backwards compatible.