It will have little impact. Many of the accounts being created now are not created through Steem Inc.
There are a plethora of instant creation services that are much more convenient to use than the regular account creation process. When you utilize another service, you will start with an account holding 3 SP (not delegated). This will be enough to transact the most basic of operations, and you will likely encumber bandwidth issues at times. It is still usable to a degree though.
That being said, even if Steem Inc. stopped account creation services altogether, it would not be a major impact for potential new users, except for the one's who don't have the liquidity to purchase an account.