I asked about upgrading GCC during the last community meeting and the answer was:

For reference, minutes from relevant community meetings:

http://merproject.org/meetings/mer-m...-04-14.33.html
http://merproject.org/meetings/mer-m...-26-08.02.html

tl;dr: Jolla has its own patches, it's unknown whether they're needed at all and are kinda shifting this all onto community (that was my impression, after all).

Btw. GCC 4.x is now end of life, even in Linaro