MSNBot will be renamed to BingBot on 1st October this year, as said by the Bing Search Blog
The whole Microsoft's Bing team has been busy in testing the beta bot since November of last year. With effect from 1st October, this beta label would be removed from the Bot and it would be renamed as BingBot.
With this report, people who have directives for MSNBot are in perplexed situation as to what directives will be obeyed by the BingBot. To this confusion, Bing has said that those who already have directives for MSNBot in their robots. txt file, BingBot will obey those directives only. However, if in another case someone has both the directives, say, one for MSNBot and the other one for BingBot, in that case Microsoft will listen to the directives for BingBot.