At least there won't be as much confusion as when the V3 came out, since Fogger 4.0 is engraved on the top cap and chimney
Looks like it'll be easier to build, and hold a bit more liquid. The dual coils will make it thirsty, though. I've been really enjoying the performance of the 2.5 I have after finding a build and filling that works for it. A bit fiddly, but it kicks out the vapor and delivers great flavor. I was planning on grabbing the V3 when the price dropped a bit, but now the V4 is out.
Best bet: have the cash to grab some V2.5 still on the market at clearance prices
while waiting for the reviews of the V4 to hit the US marketplace.