Not necessarily. I hate Man United, Inter, Real Madrid, so my natural disposition would be to support Barca in these encounters; however, were they playing Lyon, Apoel, Bordeaux, or Ajax I couldn't care less who wins.
I am just anti-English teams (except Arsenal), Real Madrid, Inter, and Bayern.
Hence, if a Barca vs Lyon final did materialize, I would watch it as a neutral, and hope they both put in a good showing regardless/irrespective of who wins.