Hi 3DSarah,
if you mean by “play full SBS 3840x1080 movies frame packed to my Sony TV” that Kodi will convert a FSBS Source (3840x1080) to a frame packed signal (1920x2205), then the answer is no to my knowledge, since Kodi will not convert between any 3D signals (except for the initial MVC → frame packed, which this thread is about). The option menu is only for selecting, what the source material is, so that Kodi can treat it properly, not to select the output format. That’s if I am not mistaken, then please correct me.
But if by “frame packed” you mean anything exceeding the normal 1920x1080 frame and consider FSBS also a “frame packed” signal (which I do not), then the answer is: Yes, if your chipset (not sure if the S905X3 is supported for 3D and how long it will be supported for CE in the future) supports this build and the TV supports the incoming signal, it will output a FSBS source as an FSBS signal. This, by the way, should already be possible in the normal builds of CE (with some quirks like broken resolution of the menu after watching something), as the new development is for MVC source material, not FSBS/TAB sources. They worked (ish) before :-).
If you would also like to take advantage of Dolby Vision in all flavors (not together with 3D, as it doesn’t exist, but for 4k Movies), then my word of advice would be to go with a S922X-J Box. This chipset is also the main chipset CE is being developed for going forward, because the newer chipsets do not support Dolby Vision (yet, and might never). If you picked for example the Ugoos Box (AM6B+) mentioned in this thread ([Guide] S922X-J (Ugoos AM6b+) CoreELEC installation and FAQs) you will be set for all formats currently available with lossless audio. It seems to become the gold standard for these kinds of boxes with CE right now.
Be aware of what Astrotrain said, 3D may in fact no make it into the main branch, but I am hopeful it will ;-). But if you only have already converted SBS material, it won’t matter to you anyways.
@Everybody: I just caught up with the thread, that happens when you go on a business trip after following the thread every day… I will do testing with the E6 approx. 24h from now when I get home, but I guess, the C6 already tested by @xmlcom is nearly identical, so it should work on the E6 without problems.