It is currently about 16.5%, plus an additional 9 times that (148.5%) is paid to SP (which gets captured by the vesting fund but released as liquid STEEM later when SP holders power down) for a total STEEM inflation rate of about 160% (scheduled to reduce to about 110%). This would be changed to a total of 9.5% of which about 8% corresponds to the rewards included in the 16.5%, and about 1.5% corresponds to the SP payments.
So to answer simply, yes the amount of STEEM produced would be cut dramatically.