they will change the rules again this year, and they will get rid of the rule that you can only participate if you are in one of the first few years of your career.
Here is why they probably changed it:
They found out that not too many people wanted to do it (none of the big stars) so they made that rule after they found that out, so it wouldn't make them look bad. If they didn't people would think
oh so and so didn't want to participate
...but in stead they will think oh they couldn't participate...this makes the league look better
If they had the old rule people would realize the dunk competition has been lame (not the participants, but the contest itself)...between them looking for new ways (unsuccessful ones) to do things (spin wheel, etc.) and other dumb things they have tried to do to boost ratings
It hasn't been drawing a lot of viewers ever since Kobe and Vince have stopped doing it...yeah, they get a good bit of people to tune in to see J-Rich...but not as many that watched to see Kobe and Vince. Another proof that rating haven't been good they got MJ to be a judge (usually current NBA players aren't judges.)
So if they find out that Vince, Kobe, and (or) T-Mac has (have) an interest in participating, then they will go back to the old rule