How about sell your PWs and 430, then buy 2 600s.
Sometimes the first and simplest answer is the best.
I have railed on Canon in other threads for their decision to abandon 580EXII owners and I still think it was a shortsighted and ill-advised decision, but despite that frustration, I can't advise anyone with just one strobe to buy either another 430EX or a 580EXII.
Since you don't have a big investment in speedliites, you are better off just biting the bullet and switching to the new 600 RT. To do it right, you will probably have to quickly invest in a ST-E3-RT so you can easily and cordlessly fire both strobes off camera.
As one who owns multiple 580EX II's this isn't an economical solution for me. Instead I've opted for the Youngnuo 622-C transceivers. But, you are probably better off cutting your small losses and switching to the 600 RT.
...Pros: future-proof, best Canon has to offer in terms of features;...
Just one comment: one might have assumed that buying Canon's top-of-the-line speedlite (580EX II) would also have been "future proof" since it was hard to imagine Canon just throwing those buyers into the ditch. We were obviously wrong.
Canon made a conscious decision with the ST-E3-RT to release only half of a product (a transmitter without a receiver). They could have easily accommodated their customers by releasing a full product (transmitter and receiver) but didn't. The moral of the story: no matter what you buy, it is only "future proof" if Canon wants it to be "future proof."