I have got 278 marks in Bitsat this year too. It is impossible to predict how low or how high the cut offs may go this year. I think you should stay until all the iterations get over. The waitlist starts at 240-250 as far as I know.

All the best!

Shivansh, 

The last year cut off for various branches in BITS PILANI were

4-Year B.E./B.Tech. Course

Chemical Engineering 280

Civil Engineering 274

Computer Science and Engineering 378

Electrical and Electronics Engineering 338

Electronics and Instrumentation Engineering 319

Manufacturing Engineering 270

Mechanical Engineering 313

4-Year B.Pharm. Course

Pharmacy 213

5-Year Integrated M.Sc. Course

Biological Sciences 259

Chemistry 265

Economics 308

Mathematics 297

Physics 288

So as you can see he can get only BPHARMA in bits pilani. 

But he can get MSC in CHEMISTRY in BITS Hyderabad and if he works hard he can change his branch next year. And MSC chemistry in BITS GOA too.

Hope it helps