It is, of course, impossible to know what might have happened. We can only guess about what human minds are capable of. However, it does seem that it would not have been possible for the Renaissance to happen without humanism.
The new ideas of humanism represented a powerful change from the past. It is not that these were completely new ideas, but they had not previously shaped society. The ideas of humanism were much more conducive to change than the previous ideas had been. It is for this reason that they were so important to the Renaissance.
In order for the Renaissance to happen, the mindset of the people had to change. It was important to be able to imagine things in new ways and it was important to rethink what people were capable of becoming. Without these changes in thinking, it is unlikely that changes in human culture and society would have been possible.