We are absolutely still a contender next year. We still have some work to do to fill out the roster, but the C's were a lucky bounce away from being tied 2-2 in that series against the Heat, which could have changed everything.
I don't think the C's will be the favorites anymore next year, but they will absolutely be a contender, and, with some chemistry clicking, and some luck, they will have a decent chance at another championship.