This is just personal opinion but I'd hate to see the Ruby GUI API
standardize on anything C++ based. I've used a few C++ UI toolkits and,
while they all worked, they were just so un-Ruby. Part of the joy of Ruby is
that you don't have to start subclassing to get anything done.

I'm very much a newbie here but the idea that you would use something as
dynamic as Ruby for the model and something as static as C++ for the UI is
just backwards. You can live with a static, strongly typed language in the
model: some would argue that it's an advantage there. Views really benefit
from dynamism and weak typing.
-- 
Adults are obsolete children.
-Dr. Seuss, humorist, illustrator, and author (1904-1991)