Ideally this film should follow what the first film did. With slight changes to allow for differences in audience taste.
In terms of plot, not much change is needed. Something slightly different in terms of why the commandos are in the Predators hunting ground, but more or less the same after that. Commandos sent in, find some corpses, kill some bad guys, walk around, Predator slaughters them, last guy channels primal instincts and shows the bastard who's boss.
This isn't the Alien series. It shouldn't have corporates or whatever trying to bag the creature behind the scenes. The Predator should basically be the
only bad guy in the film (with the exception of some faceless fodder for the commandos to kill earlier). What the movie makers should concentrate on is having the main character channel his inner primal animal to cleverly turn the Predator into his prey. If they do this right, it'll make for a great showdown.
Oh, and it needs one of these moments:
http://www.youtube.com/watch?v=XCG_ETMZvyg&feature=related If it has one of those, I'll shit a rainbow of joy.
Also...The first film came out in the 80s where testosterone movies were common place, and Predator was pretty much the big daddy of these films. Nowadays however, you don't really have many of these films. The action we have these days is much more realistic. Predator 3 could benefit from this. Having big guys who look like they fought a bear to land to role is a must, but the action can't really afford to be guys strolling round a camp firing from the hip spouting one liners. Audiences would want something more real, and I think the horror aspect of the Predator itself would be amplified if it's prey seemed somewhat less godly. Don't get me wrong, I love the fights in Predator, and in most testosterone films, but I don't think it's as suited for todays audience as it was back then.
Finally, less of that CGI shoulder cannon. It looks like ass. Bring back the blow dryer flare gun please. Seriously.