CF
Native Instruments seems to be pushing Battery out of their line,
I am not sure where you get that from, but you may be right, development of drum products seems to be focusing on Kontakt with the "Drummer" series, West Africa etc.
Updating to the 64 bit version of Battery is probably your easiest option as you are already familiar with the program and if you already have Battery 3 its probably a free update. Even if it gets discontinued you will still have quite a few years use out of it.
Are you talking about a sampler where you are going to use your own samples, as opposed to one that comes with proprietary content? If I wanted to do this I would pick Kontakt, OK its not got the drum machine like interface but at the end of the day you can still map a sample to any MIDI note an trigger it from your pads. You can map velocity layers and round robins and by splitting your samples into different instruments up to 16 output channels, add effects, write scripts. You can be as simple or as complex as you like.
Toontrack, BFD and Steven Slate will not let you map your own samples,(unless I am missing something). You can use your own samples in Session Drummer 3 however.