Yes he can continue CA and he can give CA Exams in May 2015.
He should fill the May 2015 Examination form provisionally.
Then he should apply for the revalidation of his registration in CA Final.
If any group is cleared, he will get due exemption.
Revised Scheme of Revalidation of Registration for various levels of CA Course (CPT, Intermediate (Integrated Professional Competence) Course and Final Course) :
Final students: Initial registration for Final Course is valid for 5 years. Students, who have registered for the Final Course on or before 31 st December, 2008 (including shifted students of Final (Old) Course to Final (New) Course) are required to revalidate their Final Course registration. Such students are advised to apply for revalidation before 31st December, 2013 without paying revalidation fee. In case any student fails to apply for revalidation by 31st December, 2013 he/ she then shall have to pay the prescribed revalidation fee, as stated above, after 1st January, 2014 for revalidating the registration. Fee for revalidation is Rs. 500/- for each revalidation. Each Revalidation shall be valid for 5 years. Students are required to ensure before applying for admission to Final examination that they have valid registration.
For more details :
https://220.227.161.86/29106validity-registration-CAcourse.pdf