...and if and when that happens, I will move to something else.
Right now, a default install (important to me since I maintain a handful of machines for friends, relations, etc) of most KDE-based distros does not include mono. With Gnome I have to go in and manually remove stuff, which is a pain.
There'll always be choice. Even if there is some application for which the only available/usable program is in Mono, the ultimate choice is with me, whether I use it or do without.
As for safety (your earlier comment), I don't know what you mean. Do you mean safety in a legal sense of some kind? I live in a country where most software (outside corporate use) is illegal. I could pirate anything I want and blog about it and nothing would happen.
My attitude is not prompted by worries of any kind. This is purely principle. Hence my statement about the final choice being mine: use it or do without.