1.
Being able to use other IMF or not, answer is yes.
https://mail.gnome.org/archives/desktop-devel-list/2012-May/msg00226.html
The other IMFs will likely continue to exist. They will require users to make changes to their systems to use them (just like right now if you're not using the default IMF for your distribution), and you won't have integrated preferences (just like right now).
2.
Compile time dependency of ibus (Comparing with “runtime dependency”), might or might not get dropped.
https://mail.gnome.org/archives/desktop-devel-list/2012-May/msg00193.html
So that’s all. Though “2” doesn’t completely satisfy me, but is acceptable for me.
I will still work input method on Linux and target for better user experience with input method, this is never changed.