If they ask what school/grade your child will be in next year, just be matter of fact and say he's going to be in XYZ school (no need to mention gifted) or nth grade. Then change the topic to their kids by asking about them.
This is what we do and just hope that they don't think about how old he is and decide to pursue it. If pressed, we're honest, but I'd just as soon not be pressed.
The last uncomfortable situation for me was when someone wanted to know my thoughts on enrichment and all kids being gifted. And then it went in a direction of wouldn't it be great if all kids were given enrichment and access to the same stuff as the GT kids in school. I really wasn't sure what to say that wouldn't be interpreted all wrong while still being honest.
