B.M.
personally I would get a "consultation" and then use common sense and good parenting skills-
As the pp said they may just want to monitor it and there is nothing wrong with that. Thumb sucking is a major problem as far teeth are concerned and braces will fix it but the time in them is prolonged, the mode of fixing becomes more painful and other obstacles become prevelent...
That all being said- I think as parents we like to jump on things good or bad- and sometimes we just need to listen and wait to see what they say. Our orthodontist gave us tips for getting our son off the binky (I was in braces it was not even for him) and they worked.
He has been in his field, been around the block and remember you can always say NO to any procedures or testing he wants that your not comfortable with.
Good luck-