Yeah, since I'm on a 5 right now, I'll probably just upgrade to a 64GB 5s, since the only killer feature for me right now is storage.
If that's your plan, you'd better upgrade before the iPhone 6 is released, because there will be no 64GB 5S after that. If it still exists it will most likely be maxed out at 32GB. More likely, it will be discontinued and the 5C will be upgraded with TouchID and an A7. It will probably come in an 8GB capacity model to replace the 4S in those markets the 4S still exists, and a 16GB and 32GB model as the mid-range offering. The 6 of course being the flagship may even extend to 128GB options, since iPads have had this for the last couple of generations, even the mini got it this time around.
My take, if anyone cares, on the 5.5" model is that it most likely isn't even an iPhone if it actually is a product coming to market. It could be a new iPod Touch, and if it is, it won't come with a cellular option, and will run the exact same resolution as the 4.7" iPhone. That would make sense given how the iPod Touch has been treated in the past, always a step below the iPhone generation it is released with. If it had cellular capability, it would probably have to be marketed as an iPad nano or something because it won't be given the phone app and that presents too many problems with consistency, because iPad apps on a 5.5" 16:9 screen don't work. The only place for a 5.5" anything is as an iPod Touch or gaming device.
Much more likely scenario is that the 5.5" device is a prototype that made it to an advanced stage but will never see the light of day. It was probably 4.7" or 5.5" and never both. 4.7" won out. Much like the teardrop iPhone 5 design that everyone was making renderings and mock-ups and case makers were making cases for in the build up to that release.
Too bad really, as it seems like 4" was a stop gap intermediary measure. I think we'll be seeing 4.7" as the size of the iPhone for longer than just one design generation, and if they could have just done it with the iPhone 5 right away, it probably would have had a positive impact overall, but it seems like there was a lot that just wasn't in place for it to happen from both component price and availability and software readiness perspectives. It's not like they haven't done well in any case, the financial results, sales numbers, and user experience speak for themselves, really.
Will be an interesting second half of 2014 in any case

Rumours coming very early this year, so for people like us that roam the tech rumours world, WWDC will probably be a let down as we have to wait even longer to hear anything official on hardware from Apple. Lots of stuff apparently in the pipeline, new product category rumours, new design generation for iPhone and possibly Macbook Air, wearables rumours all over the place, etc.