Good question! The TB60’s will not work with the 210. They are much bigger batteries. The TB55’s are not EOL (we haven’t heard anything from DJI) and should be around for a while considering the Matrice 200 is still sold and heavily used.
I have not heard of the TB55 being end of lifed either. However, the Matrice 200 series I imagine will begin being phased out in the near future. We also have quite a few TB55's in stock.