I'm glad that Microsoft is committed to this offering. However, my thought process to rationalize holding off on a preorder as follows:
1) I would likely try to sell my SP2 for some amount, and my loss/cost-of-use might be significant since form factor is changing. Alternatively, if I stay the course, I might be able to pick up SP/SP2 docks & accessories from SP3 early adopters on the cheap, holiday discounts, or inventory clearance.
2) haswell has been great, but even with all the advantages of SP3, I can't justify the cost of #1 without some iGPU spec bump. MS has the $ and will likely want to ship a broadwell model eventually even if SP3 doesn't sell like hotcakes. Probably a 2015 ordeal though since holiday will be reserved for discounts & bundles.
3) SP2 got a haswell slight spec bump after launch, due to inventory I suppose, so I feel somewhat burned. Irrational, I know, but I need to acknowledge it.
4) same CPU generation, same battery, bigger screen, no chargecover -- SP2 battery life for my usage was good, but unless reviews prove otherwise, I've no reason to think SP3 will have a better battery life.
5) SP2 works well. Microsoft should have sales penalized for shipping the slate & typepad separately, if it is going for "laptop". An expected retina refresh to the ultraportable macbook line will likely be priced comparably or less than SP3 w/ typecover so marketing will have fun with that.
Having said that, it doesn't mean your Surface Pro 2 is useless. It's still a great device with power to spare... for most people.
I do feel your pain a little though, I bought a Moto G just before they added the SD card slot & 4G. You've just got to come to terms with the fact that device lifetime is longer than the product cycle.