Most of the time guys won't act on what they say are going to do. Things get said in the heat of the moment and as ryan said at the end of the day it's just "words". So no it's never assault until it's gets physical. That's the way it is to most blokes won't really get too excited until it's physical then it's a whole different ball game. This was just some shit talk between a couple of guys butting heads it's quite normal with male bonding. Especially with younger guys.
Guys say shit, threaten to get the other guy to take a swing. Then they feel justified. Spending a lot of drunk nights in bars and clubs in my past this is the go to thing. Make threats, intimidate, to get the other person to come back then feel justified.
Battery is when it gets physical. Assualt is causing another person to apprehend immediate and personal violence.