Ontario has not made it explicitly clear whether they will only be sending out 2700 PT notifications. However, there will always be a few rejections and the number of PTs sent out may exceed 2700 to adjust the rejections but the number of nominations will not cross 2700 at any cost.
Having said that, many people have speculated that this might be a money making scheme as Ontario might send out 5000 PTs, issuing nomination to 2700 and keeping the money from others. This cannot be done, because this will termed as fraud and Ontario government would not want to invite lawsuits. They can only issue their "quota of 2700 nominations" and if there are rejections they can send new PTs to fill up the vacant slots.
If they want your money they can always raise the fee to 3000 CAD and many will pay that happily.
So, if you have a PT and follow the guidelines accurately, you will certainly be nominated. After all its the Ontario Government and not some shady immigration consultant trying to con you.