His assist and blocks tend to fluctuate so far in his career, but I'd say in his prime he'll get a max of 2.5 assists and 3 blocks.
His points and rebounds should definitely increase. His season average was 22.3/10.2, but he was tearing shit up after his toe surgery. Look at his last 20 games. He was basically 26/11/2/2. That's considering that he tailed off in his last 5 games, to the tune of 18/9/1.4/1.6.
So essentially he's already shown us that his prime could be at least, if not better than 26/11/2/2, if he has a fully healthy season.
With McGrady back in the lineup, I'd say his scoring doesn't stay quite as high as it was post-surgery, but I think his assists go up a little.
24/10.5/2.2/2.0 is my prediction for 06-07.