According the new update policy, I'm not sure why I can't get anymore update.
Software Number: 1.63.531.2710RD
I have no idea what you mean by "the new update policy."
However, you do have the newest software version that is currently available for the myTouch 4G Slide. T-Mobile cannot send you any updates, because you're already up-to-date!
It's a good phone though. Are you having a specific problem or bug that makes you want to update it? Is there something wrong with your software that you want help with?