I am currently in Wellington and so I am of course following what is going on.
It remains to be seen how any of it will play out, but the current outbreak is in the GP Village and the FEI barn is closed. Probably a good 5-8 miles separates Jim Brandon and the PBIEC, so that should help, and since the competition at Jim Brandon is not til next weekend it will all hopefully be sorted out by then. The whole thing is very scary, though.
Not sure what's going on dressage-wise, but you'll definitely want to to stop at the Tackeria, plus check out all the vendors @ PBIEC. There's also a nice tack/consignment shop called Silver Spur (I don't remember exactly where it is, though--??). There is a new dressage complex right down the road from PBIEC, but I don't know if there's anything going on there (I would *guess* though). Have fun-- Wellyworld is awesome!