I was hot to try the Nano Batts until I read a review on Amazon. The guy said that the new batteries will indeed “fit” the current Dewalt 18V cordless tools but because new battery is physically so much smaller than the XRP, it seems to lock in loosely and also leaves the front quarter of the tools base exposed.
This could allow dirt and debris to collect and prevents you from being able to stand or balance the tool upright on the battery, like you would sometimes do with the cordless flashlights.
I have no doubt that it was more profitable for DeWalt to do what it did, which is to design a whole new tool line around this battery system to take advantage of the smaller size, but it would have been nice if they had taken into account the millions of customers, like me, that already own thousands of dollars worth of their existing product line and would just like to upgrade to the newer battery technology.
Maybe Dewalt will release an actual retrofit version for the existing 18V tool line, but I wouldn’t count on it.
Milwaukee managed to make their new Lithium battery fit their existing 18V line. Dewalt should be able to do the same.

Regards