Exactly 619478.59338440 MSC were created and no more will ever be created.
When asked about it, I think Willet replied: "...well, I don't want to say '
never'"
What if you had the choice: the projects dies for lack of development resources - or - 10% dilution for all participants to reach a spectacular success?
I'd take choice #2.
Never say never. Or 'ever'.

More Mastercoins doesn't dilute anything if the project is a success. Development resources would come from Bitcoin once the decentralized exchange is built. I don't see how it will be an issue at all.
Also you'll have many commercial interests and venture capitalists who will pour millions into it if it even looks like its a success.
With such ample and excellent development resources, one might first question other aspects of the project.