Nope, not at all -
maybe they are interviewing more people tomorrow or later in the week
maybe one of the panel had to rush off straight after the interview and they are going to get back together to evaluate interviewees at a later point
maybe the panel needs to check some HR issue before offering the job
maybe the panel were all in meetings the rest of the day and want to sleep on the decision
and best "worse case" scenario - maybe they have offered it to someone else but that person might turn it down and so they might offer it to their second choice person!