Around 200,000 - 2,50,000 applications were expected this year for H1B quota. Probably USCIS may receive around 100k applications for advanced degree(masters) quota.

USCIS suspending the premium processing is an indication of high inflow of H1B petitions this year.

Reasons for high volume of H1B applications for FY 2018

1) Trump Effect

Trump's stand on H1B visas sent shock waves across IT industry and outsourcing companies. They are planning to apply for H1B visas this year as if there won't be new H1B visas from next year onward.

2) OPTs don't want to wait until last chance

From the past few years OPT students didn't apply for H1B immediatly after graduation as they have multiple chances of applying for H1B visa and it's safe bet to be on OPT. Due to the less probability of getting selected lottery this year, OPTs are planning to apply H1B in first attempt this year.

3) Multiple petitions by OPTs & F1/OPT is no longer safe

It's no longer safe to be on OPT as working at third party client sites is illegal. Students want to avoid using OPT as much as possible and they are trying to get H1B as soon as possible. As you know there is less chance of getting selected in lottery from past few years.

To increase the chances of getting H1B, OPT students will apply for 2-3 H1B petitions.

4) Rumors of cancellation of H4-EAD

Since last year demand for H1B Visa among H4 dependents is very low as there is H4-EAD facility for them to start working in USA. With the rumors of revoking of H4-EAD by Trump's administration, lot of H4 visa candidates are preferring to apply H1B this year.

History of number of petitions received by USCIS