Hi Chandrashekhar,
Please understand one thing clearly that being a SAP MM consultant itself requires domain knowledge of Material Managment. As you don't have any prior experience how could you justify with your career by putting 3+ yrs in to MM module.
In SAP if you are quotating yourself something wrong than i afraid that you will get ruined with the work you will get to cope with.
I don't know what height you have already reached once have worked for Testing in 7 years.
So, i will suggest you to take any decision wisely.