better future in I.T.engineering or in mechanical engineering

Dear

If you look further education into Aerospace engineering or space science research than through B.tech Mechanical branch you can pursue M.tech Aerospace engineering. And even you try for NDA into research domain and enter into DRDO section through mechanical.

And if you want to enter into design of software and related profile than choose B.tech IT

All the Best

Mechanical is always a evergreen branch as it is core branch but the situation of core is not very good at this time....
Better you should choose IT instead of mechanical