For what has changed:
Motors are pretty similar, but
more people are using mid-drives which are good for hills and might be great for you.
For a hub motor, there is a new two speed hub motor, which can help if you want to ride on hills but don't like the mid drive:
https://www.electricbike.com/2-speed-e-matic-xiongda/
Batteries - not too much change. Lithum ion seems to get a little better, and LiFePo4 has the longest life. Really, read around that web site and see what you can learn.
https://www.electricbike.com/2014-year-in-review/
some battery info:
http://www.electricbike.com/high-cur...ries-not-lipo/
http://www.electricbike.com/lithium-cobalt-manganese/