i think we all are always somewhat leary of just what our coworkers motives are up to. unfortunately there isnt much we can do about it other than to just let whatever might happen play out like its going to play out and move on from that point.
its really not going to help things any to keep yourself up in arms about being suspicious of every move everyone makes every single minute of every single day.. thats just going to upset the dynamics of the environment at work by creating tension and hostility and making it all that much more stressfull to have to work under each day.
just always remain vigilant about how you are doing your job . if you feel heeby about something that seems to be off somehow dont do a thing with it until you do a bit of double checking around to verify that the details are correct or not.
unless you know for a fact that the boss has put someone else in charge to take the lead on a project , dont fall for the words of anyone who is trying to boss you around .