1 satoshi = smallest unit, pretty much in general use today
1 bit = 100 satoshi, eventually every day use, coffee, sandwiches, etc.
1 XBT = 1 bit, should be the official symbol on all exchanges, forex, etc.
1 BTC = 1000000 bits = kept for dealing with larger amounts, may fade
That is crazy. Adding more terms doesn't make it simple. Just stick and "XBT" is a totally different term again.
kBTC = 1000 BTC
BTC
mBTC = .001 BTC
uBTC = .000001 BTC
Now that is easy and simple and follows SI standards. It can also easily extended in either direction. One term and stardard prefixes.