My daughter was an early reader and was eager to write as well, so rather than have her learn bad habits, we used Handwriting without Tears when she was 4. She learned the correct formation, but still had very messy printing. She was partly too young, and partly too impatient to take the time to do it neatly. When she was 7, I taught her cursive, in the hope that would give her a fresh start and improve things. She was still very messy.
This year, as she was 9, my son was 7, with very nice printing and wanting to learn cursive. So we all did “Teaching Cursive: This Method Works”. Even me, since I haven’t used cursive in years because no one could read it. This time DD9 was ready. I think it also helped to have me doing all the exercises along with her. Her handwriting has greatly improved. It’s still not as neat as her younger brother’s, (go figure!) but it is much nicer and she cares more. She is proud when she does a nice job, so she slows down and works more carefully.
My cursive isn’t all too bad anymore either, although I do have to remember to slow down and not grip the pencil too tightly. Oh, and I have that dreaded four-finger grip and it can work, but if the pencil grips that the others mentioned help to teach her the tripod, all the better.
All that to say: Yes, it can improve. At age 9, or, ahem, older. I highly endorse “Teaching Cursive: This Method Works.” The instructions and diagrams are very clear and understandable, and make teaching the formation easy. We have really enjoyed it.