You say backwards, I say forwards…
Backward compatible and forward compatible have specific meanings in the software world, but in collequial/conversational usage, the meanings are usually reversed.
For example, customers never ask me
Is Softimage 2012 forward compatible with Softimage 2013?
Rather, they ask me
Is Softimage 2013 backward compatible with 2012?
What the customer usually wants to know is can 2012 load a scene saved by 2013?
But that’s not backwards compatiblity, that’s forwards compatibility 😉
- Forwards compatibility = ability of older versions to load data saved by newer versions.
Softimage is not forwards compatible: it cannot load files from newer versions of Softimage
- Backwards compatibilty = ability of the new versions to load data saved by older versions.
Softimage is backwards compatible: it can load scene files [and models] saved by older versions of Softimage
In general:
- Newer versions of Softimage can load scenes and models created by older versions.
- Older versions Softimage cannot load scenes and models created by newer versions.
- Newer versions of Softimage can load plugins compiled with older versions
eX-SI 
But it would be really nice if SI support forward compatibility. It can warning me: hey you are opening newer scene so you lost this shaders, etc. For example I have to send some scenes with characters to animator, but I have to use old version 😦 for character creating etc. Fbx is not solution for me
Tongue Twister. Are you forward compatible, I cannot load a older version of myself, but I can go back to the older me, backwards compatible.