From France I believe my next stop will be to go northeast into Luxembourg. Depending on how you want to handle things and on pricing it might be best at this point to get a Euro Rail pass of some kind so you can more easily make reservations and travel without having to worry about a car through all of Europe. If needed you can always rent one for a day wherever you are.
We go to the city of Luxembourg (yes the same name as the country). There are a number of absolutely fascinating things about this country and city. There are parts of the city where you can see 1000 years of history and architecture in a 2 hour walk.
In Luxembourg you can also do a fair amount of wine tasting in the Moselle Valley. There are a number of wine and grape festivals that run in various cities throughout the fall.
One more thing near and dear to my heart is the food. According to VisitLuxembourg.com there are more Michelin Star restaurants per capita than any other country in the world. While I am all about tasting and enjoying the local food that normal people eat I have no problem with the occasional really nice meal. This is a dream trip after all.