Below is a quote from Alan about what he has found out so far, not confirmed.
I've been fishing hard for bits and pieces of information over the past few days, and here is what I got so far:
New finishing process that's supposed to increase corrosion resistance dramatically.
New spool and lip design, and new coating process- Apparently Shimano received an increasing number of complaints about pitting appearing where the lip meets the spool on current SW reels.
CI4+ rotor! That's Shimano's version of Daiwa's Zaion composite.
New stronger oscillation gears - Probably they can afford the extra heft with the weight they cut on the rotor.
Better positioned drive gear that's less offset for better efficiency.
These are from more than one source, based on prototypes, with varied degrees of credibility. I'd say all in all it's 85% credible, so take it for what it's worth. I initially thought I should just keep to myself until I get something that's 100% credible, but then I said what the heck, I'll just share it because it's all about our fun tackle addiction and no one will die if the actual production reels eventually had different features
I'll keep my ears wide open and if you know or hear something, you know how to reach me!
The whole link.
http://jignpopforum.com/topic/649-next-generation-stella-sw/