Heres a little sneak peak on 6.0s...watch the videos here..and the guy thats out hitting the other guy 6.0, and the other guy is a 4.0..hey look you're around there..so you can see how much you need to improve.
http://tt.tennis-warehouse.com/showthread.php?t=291604
Its not impossible to do (0.00000001%
)..but i doubt it's ever been done in a year..or 2..
You're saying you want to go from 3.5 which is around high jv / low varsity in highschool level (depends on your school), to being able to compete and do well against D1 students in a year. If you could do that..i'd say you might have the potential to get 20+ grandslams :shock:. The learning curve is high at the beginning for everyone, but as you increase your level the curve slowly gets smaller and smaller...some stop improving, some keep improving but a bit slower, some improve very slowly...
To me, a lot of people look like they have potential in the first 3 years or so..including a lot of amazing little 8 year olds on youtube, but it's those who are improving at a higher level pretty quickly that have real potential to become one of the best. A lot of highly potential kids..either hit slumps and give up, get injured, stop trying, etc. But your chances aren't 0, so goodluck..but have school as a fallback plan if tennis doesnt work..