Dry cleaning will only permanently press in a hem line even further.
After fully removing the old stitches, wet the jeans on both side and carefully press until flat. Then launder them, and after drying, repeat the wet pressing process.
If all else fails and you simply can't remove the old line, you have a few creative options:
1- you can stonewash the jeans so as to bring the denim into a more evenly distributed coloration;
2- if you're young enough or into the new trimmed look, you can add a decorative trim to the new hemline and to make the jeans NOT look as tho you added this, add the same embellishment to another area of the jeans, such as the upper back pocket trimline;
3- you can try to match the denim as closely as possible through a small bit of purchased fabric and cuff them.
I suspect there are other alternatives which other members can offer up as well. And as a sewer, you probably have a few ideas of your own. Look through fashion mags and get a sense of what's out there, and merely play and duplicate.