Hi Pradeep,
So far BEx query result are saved as .xls for me, might be next releases you might get an option to save as .xlsx.
Let me understand, why do you want .xlsx? is there any issue/problem with .xls?
You can try Analysis Office tool to run bex reports and you can save it as .xlsx. Which is similar to BEx analyzer.
As you mentioned as of now, converting .xls file extention to .xlsx is only the option as of now.
Thanks,
Umashankar