At least according to a few software engineers I asked about this subject, symantec and wind river doesn't offer something unique security-related. It's mostly branding.
I wonder if this is the only benefit for this chip, or are there others planned?
Getting better opportunities on the security and embedded internet stack because of very long stay in the computing environment will be a very good plus point for Intel on getting proven in IoT Processor segment.
I don't know anything, except that AMD64 introduced a lot more than just a bigger address space. IA32 is really not a good/modern ISA, and it would be quite strange to see Intel falling back 10+ years. one real register, stack-based x87, no vectorization, etc. at the time, 64b extensions were justified as not adding a lot of chip complexity - of course that's relative to OoO/superscalar stuff.